diff --git a/libguile/ChangeLog b/libguile/ChangeLog
index 37b648c49..b280678d2 100644
--- a/libguile/ChangeLog
+++ b/libguile/ChangeLog
@@ -1,5 +1,13 @@
 2002-12-10  Mikael Djurfeldt  <mdj@kvast.blakulla.net>
 
+	* gc-malloc.c (malloc_mutex): New mutex.
+	(scm_gc_init_malloc): Initialize it.
+	(scm_realloc): Serialize call to realloc
+	(scm_calloc): Same for calloc.
+	Thanks to Wolfgang Jaehrling!
+	(Now we have to make sure all calls to malloc/realloc are made
+	through scm_malloc.)
+
 	* threads.c (really_launch): Release heap (to prevent deadlock).
 	(create_thread): Release heap before locking thread admin mutex.
 
diff --git a/libguile/gc-malloc.c b/libguile/gc-malloc.c
index dd7e30432..f6138f89f 100644
--- a/libguile/gc-malloc.c
+++ b/libguile/gc-malloc.c
@@ -99,6 +99,8 @@ extern unsigned long * __libc_ia64_register_backing_store_base;
 
 static int scm_i_minyield_malloc;
 
+static scm_t_mutex malloc_mutex;
+
 void
 scm_gc_init_malloc (void)
 {
@@ -114,6 +116,8 @@ scm_gc_init_malloc (void)
 
   if (scm_mtrigger < 0)
     scm_mtrigger = SCM_DEFAULT_INIT_MALLOC_LIMIT;
+
+  scm_i_plugin_mutex_init (&malloc_mutex, 0);
 }
 
 
@@ -126,7 +130,9 @@ scm_realloc (void *mem, size_t size)
 {
   void *ptr;
 
+  scm_i_plugin_mutex_lock (&malloc_mutex);
   SCM_SYSCALL (ptr = realloc (mem, size));
+  scm_i_plugin_mutex_lock (&malloc_mutex);
   if (ptr)
     return ptr;
 
@@ -134,7 +140,9 @@ scm_realloc (void *mem, size_t size)
   
   scm_i_sweep_all_segments ("realloc");
   
+  scm_i_plugin_mutex_lock (&malloc_mutex);
   SCM_SYSCALL (ptr = realloc (mem, size));
+  scm_i_plugin_mutex_unlock (&malloc_mutex);
   if (ptr)
     { 
       scm_i_thread_wake_up ();
@@ -146,7 +154,9 @@ scm_realloc (void *mem, size_t size)
   
   scm_i_thread_wake_up ();
   
+  scm_i_plugin_mutex_lock (&malloc_mutex);
   SCM_SYSCALL (ptr = realloc (mem, size));
+  scm_i_plugin_mutex_unlock (&malloc_mutex);
   if (ptr)
     return ptr;
 
@@ -172,7 +182,9 @@ scm_calloc (size_t sz)
     By default, try to use calloc, as it is likely more efficient than
     calling memset by hand.
    */
+  scm_i_plugin_mutex_lock (&malloc_mutex);
   SCM_SYSCALL(ptr= calloc (sz, 1));
+  scm_i_plugin_mutex_unlock (&malloc_mutex);
   if (ptr)
     return ptr;