diff --git a/src/freelist.h b/src/freelist.h
new file mode 100644
index 000000000..6eec6dbac
--- /dev/null
+++ b/src/freelist.h
@@ -0,0 +1,31 @@
+#ifndef FREELIST_H
+#define FREELIST_H
+
+// A size-segregated freelist with linear-log buckets à la
+// https://pvk.ca/Blog/2015/06/27/linear-log-bucketing-fast-versatile-simple/.
+
+#include "gc-assert.h"
+#include "gc-histogram.h"
+
+#include <string.h>
+
+#define DEFINE_FREELIST(name, max_value_bits, precision, node)          \
+  struct name { node buckets[((max_value_bits) << (precision)) + 1]; }; \
+  static inline size_t name##_num_size_classes(void) {                  \
+    return ((max_value_bits) << (precision)) + 1;                       \
+  }                                                                     \
+  static inline uint64_t name##_bucket_min_val(size_t idx) {            \
+    GC_ASSERT(idx < name##_num_size_classes());                         \
+    return gc_histogram_bucket_min_val((precision), idx);               \
+  }                                                                     \
+  static inline void name##_init(struct name *f) {                      \
+    memset(f, 0, sizeof(*f));                                           \
+  }                                                                     \
+  static inline size_t name##_size_class(uint64_t val) {                \
+    return gc_histogram_bucket((max_value_bits), (precision), val);     \
+  }                                                                     \
+  static inline node* name##_bucket(struct name *f, uint64_t val) {     \
+    return &f->buckets[name##_size_class(val)];                         \
+  }
+
+#endif // FREELIST_H
diff --git a/src/large-object-space.h b/src/large-object-space.h
index 18e6280da..703c048b4 100644
--- a/src/large-object-space.h
+++ b/src/large-object-space.h
@@ -6,7 +6,6 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
-#include <sys/mman.h>
 #include <unistd.h>
 
 #include "gc-assert.h"
@@ -14,6 +13,8 @@
 #include "gc-conservative-ref.h"
 #include "address-map.h"
 #include "address-set.h"
+#include "background-thread.h"
+#include "freelist.h"
 
 // Logically the large object space is a treadmill space -- somewhat like a
 // copying collector, in that we allocate into tospace, and collection flips
@@ -23,42 +24,87 @@
 
 struct gc_heap;
 
+struct large_object {
+  uintptr_t addr;
+  size_t size;
+};
+struct large_object_node;
+struct large_object_live_data {
+  uint8_t is_survivor;
+};
+struct large_object_dead_data {
+  uint8_t age;
+  struct large_object_node **prev;
+  struct large_object_node *next;
+};
+struct large_object_data {
+  uint8_t is_live;
+  union {
+    struct large_object_live_data live;
+    struct large_object_dead_data dead;
+  };
+};
+
+#define SPLAY_TREE_PREFIX large_object_
+typedef struct large_object large_object_key_span;
+typedef uintptr_t large_object_key;
+typedef struct large_object_data large_object_value;
+static inline int
+large_object_compare(uintptr_t addr, struct large_object obj) {
+  if (addr < obj.addr) return -1;
+  if (addr - obj.addr < obj.size) return 0;
+  return 1;
+}
+static inline uintptr_t
+large_object_span_start(struct large_object obj) {
+  return obj.addr;
+}
+#include "splay-tree.h"
+
+DEFINE_FREELIST(large_object_freelist, sizeof(uintptr_t) * 8 - 1, 2,
+                struct large_object_node*);
+
 struct large_object_space {
+  // Access to all members protected by lock.
   pthread_mutex_t lock;
 
+  // Splay tree of objects, keyed by <addr, size> tuple.  Useful when
+  // looking up object-for-address.
+  struct large_object_tree object_tree;
+  // Hash table of objects, where values are pointers to splay tree
+  // nodes.  Useful when you have the object address and just want to
+  // check something about it (for example its size).
+  struct address_map object_map;
+
+  // Size-segregated freelist of dead objects.  Allocations are first
+  // served from the quarantine freelist before falling back to the OS
+  // if needed.  Collected objects spend a second or two in quarantine
+  // before being returned to the OS.  This is an optimization to avoid
+  // mucking about too much with the TLB and so on.
+  struct large_object_freelist quarantine;
+
   size_t page_size;
   size_t page_size_log2;
   size_t total_pages;
   size_t free_pages;
   size_t live_pages_at_last_collection;
   size_t pages_freed_by_last_collection;
+  int synchronous_release;
 
-  struct address_set from_space;
-  struct address_set to_space;
-  struct address_set survivor_space;
+  // A partition of the set of live objects into three sub-spaces.  If
+  // all collections are major, the survivor space will always be empty.
+  // The values of these maps are splay tree nodes.
+  struct address_map from_space;
+  struct address_map to_space;
+  struct address_map survivor_space;
+
+  // Set of edges from lospace that may reference young objects,
+  // possibly in other spaces.
   struct address_set remembered_edges;
-  struct address_set free_space;
-  struct address_map object_pages; // for each object: size in pages.
-  struct address_map predecessors; // subsequent addr -> object addr
 };
 
-static int large_object_space_init(struct large_object_space *space,
-                                   struct gc_heap *heap) {
-  pthread_mutex_init(&space->lock, NULL);
-  space->page_size = getpagesize();
-  space->page_size_log2 = __builtin_ctz(space->page_size);
-  address_set_init(&space->from_space);
-  address_set_init(&space->to_space);
-  address_set_init(&space->survivor_space);
-  address_set_init(&space->remembered_edges);
-  address_set_init(&space->free_space);
-  address_map_init(&space->object_pages);
-  address_map_init(&space->predecessors);
-  return 1;
-}
-
-static size_t large_object_space_npages(struct large_object_space *space,
-                                       size_t bytes) {
+static size_t
+large_object_space_npages(struct large_object_space *space, size_t bytes) {
   return (bytes + space->page_size - 1) >> space->page_size_log2;
 }
 
@@ -67,66 +113,105 @@ large_object_space_size_at_last_collection(struct large_object_space *space) {
   return space->live_pages_at_last_collection << space->page_size_log2;
 }
 
-static inline int large_object_space_contains(struct large_object_space *space,
-                                              struct gc_ref ref) {
+static inline int
+large_object_space_contains(struct large_object_space *space,
+                            struct gc_ref ref) {
   pthread_mutex_lock(&space->lock);
-  // ptr might be in fromspace or tospace.  Just check the object_pages table, which
-  // contains both, as well as object_pages for free blocks.
-  int ret = address_map_contains(&space->object_pages, gc_ref_value(ref));
+  int ret = address_map_contains(&space->object_map, gc_ref_value(ref));
   pthread_mutex_unlock(&space->lock);
   return ret;
 }
 
-static void large_object_space_flip_survivor(uintptr_t addr,
-                                             void *data) {
-  struct large_object_space *space = data;
-  address_set_add(&space->from_space, addr);
+static inline struct gc_ref
+large_object_space_contains_edge(struct large_object_space *space,
+                                 struct gc_edge edge) {
+  pthread_mutex_lock(&space->lock);
+  struct large_object_node *node =
+    large_object_tree_lookup(&space->object_tree, gc_edge_address(edge));
+  uintptr_t addr = node ? node->key.addr : 0;
+  pthread_mutex_unlock(&space->lock);
+  return gc_ref(addr);
 }
 
-static void large_object_space_start_gc(struct large_object_space *space,
-                                        int is_minor_gc) {
+static void
+large_object_space_flip_survivor(uintptr_t addr, uintptr_t node_bits,
+                                 void *data) {
+  struct large_object_space *space = data;
+  struct large_object_node *node = (void*)node_bits;
+  GC_ASSERT(node->value.is_live && node->value.live.is_survivor);
+  node->value.live.is_survivor = 0;
+  address_map_add(&space->from_space, addr, (uintptr_t)node);
+}
+
+static void
+large_object_space_start_gc(struct large_object_space *space, int is_minor_gc) {
   // Flip.  Note that when we flip, fromspace is empty, but it might have
   // allocated storage, so we do need to do a proper swap.
-  struct address_set tmp;
+  struct address_map tmp;
   memcpy(&tmp, &space->from_space, sizeof(tmp));
   memcpy(&space->from_space, &space->to_space, sizeof(tmp));
   memcpy(&space->to_space, &tmp, sizeof(tmp));
   
   if (!is_minor_gc) {
-    address_set_for_each(&space->survivor_space,
+    address_map_for_each(&space->survivor_space,
                          large_object_space_flip_survivor, space);
-    address_set_clear(&space->survivor_space);
+    address_map_clear(&space->survivor_space);
     space->live_pages_at_last_collection = 0;
   }
 }
 
-static int large_object_space_copy(struct large_object_space *space,
-                                   struct gc_ref ref) {
+static inline size_t
+large_object_space_object_size(struct large_object_space *space,
+                               struct gc_ref ref) {
+  uintptr_t node_bits =
+    address_map_lookup(&space->object_map, gc_ref_value(ref), 0);
+  GC_ASSERT(node_bits);
+  struct large_object_node *node = (struct large_object_node*) node_bits;
+  return node->key.size;
+}
+
+static void
+large_object_space_do_copy(struct large_object_space *space,
+                           struct large_object_node *node) {
+  GC_ASSERT(address_map_contains(&space->from_space, node->key.addr));
+  GC_ASSERT(node->value.is_live);
+  GC_ASSERT(!node->value.live.is_survivor);
+  uintptr_t addr = node->key.addr;
+  size_t bytes = node->key.size;
+  uintptr_t node_bits = (uintptr_t)node;
+  space->live_pages_at_last_collection += bytes >> space->page_size_log2;
+  address_map_remove(&space->from_space, addr);
+  if (GC_GENERATIONAL) {
+    node->value.live.is_survivor = 1;
+    address_map_add(&space->survivor_space, addr, node_bits);
+  } else {
+    address_map_add(&space->to_space, addr, node_bits);
+  }
+}
+
+static int
+large_object_space_copy(struct large_object_space *space, struct gc_ref ref) {
   int copied = 0;
   uintptr_t addr = gc_ref_value(ref);
   pthread_mutex_lock(&space->lock);
-  if (!address_set_contains(&space->from_space, addr))
-    // Already copied; object is grey or black.
-    goto done;
-  space->live_pages_at_last_collection +=
-    address_map_lookup(&space->object_pages, addr, 0);
-  address_set_remove(&space->from_space, addr);
-  address_set_add(GC_GENERATIONAL ? &space->survivor_space : &space->to_space,
-                  addr);
-  // Object is grey; place it on mark stack to visit its fields.
-  copied = 1;
-done:
+  uintptr_t node_bits = address_map_lookup(&space->from_space, addr, 0);
+  if (node_bits) {
+    large_object_space_do_copy(space, (struct large_object_node*) node_bits);
+    // Object is grey; place it on mark stack to visit its fields.
+    copied = 1;
+  }
   pthread_mutex_unlock(&space->lock);
   return copied;
 }
 
-static int large_object_space_is_copied(struct large_object_space *space,
-                                        struct gc_ref ref) {
+static int
+large_object_space_is_copied(struct large_object_space *space,
+                             struct gc_ref ref) {
   GC_ASSERT(large_object_space_contains(space, ref));
   int copied = 0;
   uintptr_t addr = gc_ref_value(ref);
   pthread_mutex_lock(&space->lock);
-  copied = !address_set_contains(&space->from_space, addr);
+  copied = !address_map_contains(&space->from_space, addr);
   pthread_mutex_unlock(&space->lock);
   return copied;
 }
@@ -134,11 +219,12 @@ static int large_object_space_is_copied(struct large_object_space *space,
 static int
 large_object_space_is_survivor_with_lock(struct large_object_space *space,
                                          struct gc_ref ref) {
-  return address_set_contains(&space->survivor_space, gc_ref_value(ref));
+  return address_map_contains(&space->survivor_space, gc_ref_value(ref));
 }
 
-static int large_object_space_is_survivor(struct large_object_space *space,
-                                          struct gc_ref ref) {
+static int
+large_object_space_is_survivor(struct large_object_space *space,
+                               struct gc_ref ref) {
   GC_ASSERT(large_object_space_contains(space, ref));
   pthread_mutex_lock(&space->lock);
   int old = large_object_space_is_survivor_with_lock(space, ref);
@@ -146,9 +232,11 @@ static int large_object_space_is_survivor(struct large_object_space *space,
   return old;
 }
 
-static int large_object_space_remember_edge(struct large_object_space *space,
-                                            struct gc_ref obj,
-                                            struct gc_edge edge) {
+static int
+large_object_space_remember_edge(struct large_object_space *space,
+                                 struct gc_ref obj,
+                                 struct gc_edge edge) {
+  GC_ASSERT(large_object_space_contains(space, obj));
   int remembered = 0;
   uintptr_t edge_addr = gc_edge_address(edge);
   pthread_mutex_lock(&space->lock);
@@ -171,61 +259,78 @@ static int large_object_space_mark_object(struct large_object_space *space,
   return large_object_space_copy(space, ref);
 }
 
-static inline size_t large_object_space_object_size(struct large_object_space *space,
-                                                    struct gc_ref ref) {
-  size_t npages = address_map_lookup(&space->object_pages,
-                                     gc_ref_value(ref), 0);
-  GC_ASSERT(npages != 0);
-  return npages * space->page_size;
+static void
+large_object_space_add_to_freelist(struct large_object_space *space,
+                                   struct large_object_node *node) {
+  node->value.is_live = 0;
+  struct large_object_dead_data *data = &node->value.dead;
+  memset(data, 0, sizeof(*data));
+  data->age = 0;
+  struct large_object_node **bucket =
+    large_object_freelist_bucket(&space->quarantine, node->key.size);
+  data->next = *bucket;
+  if (data->next)
+    data->next->value.dead.prev = &data->next;
+  data->prev = bucket;
+  *bucket = node;
 }
 
-static void large_object_space_reclaim_one(uintptr_t addr, void *data) {
+static void
+large_object_space_remove_from_freelist(struct large_object_space *space,
+                                        struct large_object_node *node) {
+  GC_ASSERT(!node->value.is_live);
+  struct large_object_dead_data *dead = &node->value.dead;
+  GC_ASSERT(dead->prev);
+  if (dead->next)
+    dead->next->value.dead.prev = dead->prev;
+  *dead->prev = dead->next;
+}
+
+static void
+large_object_space_reclaim_one(uintptr_t addr, uintptr_t node_bits,
+                               void *data) {
   struct large_object_space *space = data;
-  size_t npages = address_map_lookup(&space->object_pages, addr, 0);
-  // Release the pages to the OS, and cause them to be zero on next use.
-  madvise((void*) addr, npages * space->page_size, MADV_DONTNEED);
-  size_t did_merge = 0;
-  uintptr_t pred = address_map_lookup(&space->predecessors, addr, 0);
-  uintptr_t succ = addr + npages * space->page_size;
-  if (pred && address_set_contains(&space->free_space, pred)) {
-    // Merge with free predecessor.
-    address_map_remove(&space->predecessors, addr);
-    address_map_remove(&space->object_pages, addr);
-    addr = pred;
-    npages += address_map_lookup(&space->object_pages, addr, 0);
-    did_merge = 1;
-  } else {
-    // Otherwise this is a new free object.
-    address_set_add(&space->free_space, addr);
-  }
-  if (address_set_contains(&space->free_space, succ)) {
-    // Merge with free successor.
-    size_t succ_npages = address_map_lookup(&space->object_pages, succ, 0);
-    address_map_remove(&space->predecessors, succ);
-    address_map_remove(&space->object_pages, succ);
-    address_set_remove(&space->free_space, succ);
-    npages += succ_npages;
-    succ += succ_npages * space->page_size;
-    did_merge = 1;
-  }
-  if (did_merge) {
-    // Update extents.
-    address_map_add(&space->object_pages, addr, npages);
-    address_map_add(&space->predecessors, succ, addr);
-  }
+  struct large_object_node *node = (struct large_object_node*) node_bits;
+  GC_ASSERT(node->value.is_live);
+  large_object_space_add_to_freelist(space, node);
 }
 
-static void large_object_space_finish_gc(struct large_object_space *space,
-                                         int is_minor_gc) {
+static void
+large_object_space_process_quarantine(void *data) {
+  struct large_object_space *space = data;
   pthread_mutex_lock(&space->lock);
-  address_set_for_each(&space->from_space, large_object_space_reclaim_one,
+  for (size_t idx = 0; idx < large_object_freelist_num_size_classes(); idx++) {
+    struct large_object_node **link = &space->quarantine.buckets[idx];
+    for (struct large_object_node *node = *link; node; node = *link) {
+      GC_ASSERT(!node->value.is_live);
+      if (++node->value.dead.age < 2) {
+        link = &node->value.dead.next;
+      } else {
+        struct large_object obj = node->key;
+        large_object_space_remove_from_freelist(space, node);
+        address_map_remove(&space->object_map, obj.addr);
+        large_object_tree_remove(&space->object_tree, obj.addr);
+        gc_platform_release_memory((void*)obj.addr, obj.size);
+      }
+    }
+  }
+  pthread_mutex_unlock(&space->lock);
+}
+
+static void
+large_object_space_finish_gc(struct large_object_space *space,
+                             int is_minor_gc) {
+  pthread_mutex_lock(&space->lock);
+  address_map_for_each(&space->from_space, large_object_space_reclaim_one,
                        space);
-  address_set_clear(&space->from_space);
+  address_map_clear(&space->from_space);
   size_t free_pages =
     space->total_pages - space->live_pages_at_last_collection;
   space->pages_freed_by_last_collection = free_pages - space->free_pages;
   space->free_pages = free_pages;
   pthread_mutex_unlock(&space->lock);
+  if (space->synchronous_release)
+    large_object_space_process_quarantine(space);
 }
 
 static void
@@ -242,14 +347,9 @@ large_object_space_mark_conservative_ref(struct large_object_space *space,
                                          int possibly_interior) {
   uintptr_t addr = gc_conservative_ref_value(ref);
 
-  if (possibly_interior) {
-    // FIXME: This only allows interior pointers within the first page.
-    // BDW-GC doesn't have all-interior-pointers on for intraheap edges
-    // or edges originating in static data but by default does allow
-    // them from stack edges; probably we should too.
-    addr &= ~(space->page_size - 1);
-  } else {
+  if (!possibly_interior) {
     // Addr not aligned on page boundary?  Not a large object.
+    // Otherwise strip the displacement to obtain the true base address.
     uintptr_t displacement = addr & (space->page_size - 1);
     if (!gc_is_valid_conservative_ref_displacement(displacement))
       return gc_ref_null();
@@ -257,59 +357,63 @@ large_object_space_mark_conservative_ref(struct large_object_space *space,
   }
 
   pthread_mutex_lock(&space->lock);
-  // ptr might be in fromspace or tospace.  Just check the object_pages table, which
-  // contains both, as well as object_pages for free blocks.
-  int found = address_map_contains(&space->object_pages, addr);
+  struct large_object_node *node = NULL;
+  if (possibly_interior) {
+    node = large_object_tree_lookup(&space->object_tree, addr);
+    if (node && !address_map_contains(&space->from_space, node->key.addr))
+      node = NULL;
+  } else {
+    uintptr_t node_bits = address_map_lookup(&space->from_space, addr, 0);
+    node = (struct large_object_node*) node_bits;
+  }
+  struct gc_ref ret = gc_ref_null();
+  if (node) {
+    large_object_space_do_copy(space, node);
+    ret = gc_ref(node->key.addr);
+  }
   pthread_mutex_unlock(&space->lock);
 
-  if (found && large_object_space_copy(space, gc_ref(addr)))
-    return gc_ref(addr);
-
-  return gc_ref_null();
+  return ret;
 }
 
-struct large_object_space_candidate {
-  struct large_object_space *space;
-  size_t min_npages;
-  uintptr_t addr;
-  size_t npages;
-};
-
-static int large_object_space_best_fit(uintptr_t addr, void *data) {
-  struct large_object_space_candidate *found = data;
-  size_t npages = address_map_lookup(&found->space->object_pages, addr, 0);
-  if (npages < found->min_npages)
-    return 0;
-  if (npages >= found->npages)
-    return 0;
-  found->addr = addr;
-  found->npages = npages;
-  return found->min_npages == npages;
-}
-    
-static void* large_object_space_alloc(struct large_object_space *space,
-                                      size_t npages) {
-  void *ret;
+static void*
+large_object_space_alloc(struct large_object_space *space, size_t npages) {
+  void *ret = NULL;
   pthread_mutex_lock(&space->lock);
-  ret = NULL;
-  struct large_object_space_candidate found = { space, npages, 0, -1 };
-  address_set_find(&space->free_space, large_object_space_best_fit, &found);
-  if (found.addr) {
-    uintptr_t addr = found.addr;
-    ret = (void*)addr;
-    address_set_remove(&space->free_space, addr);
-    address_set_add(&space->to_space, addr);
+  
+  size_t size = npages << space->page_size_log2;
+  for (size_t idx = large_object_freelist_size_class(size);
+       idx < large_object_freelist_num_size_classes();
+       idx++) {
+    struct large_object_node *node = space->quarantine.buckets[idx];
+    while (node && node->key.size < size)
+      node = node->value.dead.next;
+    if (node) {
+      // We found a suitable hole in quarantine.  Unlink it from the
+      // freelist.
+      large_object_space_remove_from_freelist(space, node);
 
-    if (found.npages > npages) {
-      uintptr_t succ = addr + npages * space->page_size;
-      uintptr_t succ_succ = succ + (found.npages - npages) * space->page_size;
-      address_map_add(&space->object_pages, addr, npages);
-      address_map_add(&space->object_pages, succ, found.npages - npages);
-      address_set_add(&space->free_space, succ);
-      address_map_add(&space->predecessors, succ, addr);
-      address_map_add(&space->predecessors, succ_succ, succ);
+      // Mark the hole as live.
+      node->value.is_live = 1;
+      memset(&node->value.live, 0, sizeof(node->value.live));
+
+      // If the hole is actually too big, trim its tail.
+      if (node->key.size > size) {
+        struct large_object tail = {node->key.addr + size, node->key.size - size};
+        struct large_object_data tail_value = {0,};
+        node->key.size = size;
+        struct large_object_node *tail_node =
+          large_object_tree_insert(&space->object_tree, tail, tail_value);
+        large_object_space_add_to_freelist(space, tail_node);
+      }
+
+      // Add the object to tospace.
+      address_map_add(&space->to_space, node->key.addr, (uintptr_t)node);
+    
+      space->free_pages -= npages;
+      ret = (void*)node->key.addr;
+      break;
     }
-    space->free_pages -= npages;
   }
   pthread_mutex_unlock(&space->lock);
   return ret;
@@ -320,18 +424,55 @@ large_object_space_obtain_and_alloc(struct large_object_space *space,
                                     size_t npages) {
   size_t bytes = npages * space->page_size;
   void *ret = gc_platform_acquire_memory(bytes, 0);
-  if (ret == MAP_FAILED)
+  if (!ret)
     return NULL;
 
   uintptr_t addr = (uintptr_t)ret;
+  struct large_object k = { addr, bytes };
+  struct large_object_data v = {0,};
+  v.is_live = 1;
+  v.live.is_survivor = 0;
+
   pthread_mutex_lock(&space->lock);
-  address_map_add(&space->object_pages, addr, npages);
-  address_map_add(&space->predecessors, addr + bytes, addr);
-  address_set_add(&space->to_space, addr);
+  struct large_object_node *node =
+    large_object_tree_insert(&space->object_tree, k, v);
+  uintptr_t node_bits = (uintptr_t)node;
+  address_map_add(&space->object_map, addr, node_bits);
+  address_map_add(&space->to_space, addr, node_bits);
   space->total_pages += npages;
   pthread_mutex_unlock(&space->lock);
 
   return ret;
 }
 
+static int
+large_object_space_init(struct large_object_space *space,
+                        struct gc_heap *heap,
+                        struct gc_background_thread *thread) {
+  memset(space, 0, sizeof(*space));
+  pthread_mutex_init(&space->lock, NULL);
+
+  space->page_size = getpagesize();
+  space->page_size_log2 = __builtin_ctz(space->page_size);
+
+  large_object_tree_init(&space->object_tree);
+  address_map_init(&space->object_map);
+
+  large_object_freelist_init(&space->quarantine);
+
+  address_map_init(&space->from_space);
+  address_map_init(&space->to_space);
+  address_map_init(&space->survivor_space);
+  address_set_init(&space->remembered_edges);
+
+  if (thread)
+    gc_background_thread_add_task(thread, GC_BACKGROUND_TASK_START,
+                                  large_object_space_process_quarantine,
+                                  space);
+  else
+    space->synchronous_release = 1;
+
+  return 1;
+}
+
 #endif // LARGE_OBJECT_SPACE_H
diff --git a/src/mmc.c b/src/mmc.c
index 68a811947..d123c4793 100644
--- a/src/mmc.c
+++ b/src/mmc.c
@@ -1127,7 +1127,8 @@ gc_init(const struct gc_options *options, struct gc_stack_addr *stack_base,
     return 0;
   }
   
-  if (!large_object_space_init(heap_large_object_space(*heap), *heap))
+  if (!large_object_space_init(heap_large_object_space(*heap), *heap,
+                               (*heap)->background_thread))
     GC_CRASH();
 
   *mut = calloc(1, sizeof(struct gc_mutator));
diff --git a/src/pcc.c b/src/pcc.c
index 6b8a55c03..9b2a8baf2 100644
--- a/src/pcc.c
+++ b/src/pcc.c
@@ -661,7 +661,8 @@ int gc_init(const struct gc_options *options, struct gc_stack_addr *stack_base,
     return 0;
   }
   
-  if (!large_object_space_init(heap_large_object_space(*heap), *heap))
+  if (!large_object_space_init(heap_large_object_space(*heap), *heap,
+                               (*heap)->background_thread))
     GC_CRASH();
 
   *mut = calloc(1, sizeof(struct gc_mutator));
diff --git a/src/semi.c b/src/semi.c
index 725a75f30..29cb0c92f 100644
--- a/src/semi.c
+++ b/src/semi.c
@@ -674,7 +674,8 @@ int gc_init(const struct gc_options *options, struct gc_stack_addr *stack_base,
 
   if (!semi_space_init(heap_semi_space(*heap), *heap))
     return 0;
-  if (!large_object_space_init(heap_large_object_space(*heap), *heap))
+  struct gc_background_thread *thread = NULL;
+  if (!large_object_space_init(heap_large_object_space(*heap), *heap, thread))
     return 0;
   
   // Ignore stack base, as we are precise.