diff --git a/libguile/async.h b/libguile/async.h
index a81a98d74..3c1725f9f 100644
--- a/libguile/async.h
+++ b/libguile/async.h
@@ -58,20 +58,18 @@ void scm_dynwind_unblock_asyncs (void);
    the manual.
 */
 
-/* Defined in threads.c.  scm_i_critical_section_level is only used
-   for error checking and will go away eventually. */
+/* Defined in threads.c. */
 extern scm_i_pthread_mutex_t scm_i_critical_section_mutex;
-extern int scm_i_critical_section_level;
 
 #define SCM_CRITICAL_SECTION_START \
   do { \
     scm_i_pthread_mutex_lock (&scm_i_critical_section_mutex);\
     SCM_I_CURRENT_THREAD->block_asyncs++; \
-    scm_i_critical_section_level++; \
+    SCM_I_CURRENT_THREAD->critical_section_level++; \
   } while (0)
 #define SCM_CRITICAL_SECTION_END \
   do { \
-    scm_i_critical_section_level--; \
+    SCM_I_CURRENT_THREAD->critical_section_level--; \
     SCM_I_CURRENT_THREAD->block_asyncs--; \
     scm_i_pthread_mutex_unlock (&scm_i_critical_section_mutex); \
     scm_async_click ();	\
diff --git a/libguile/continuations.c b/libguile/continuations.c
index 74bb9112f..69d2569da 100644
--- a/libguile/continuations.c
+++ b/libguile/continuations.c
@@ -256,7 +256,7 @@ scm_dynthrow (SCM cont, SCM val)
   SCM_STACKITEM *dst = thread->continuation_base;
   SCM_STACKITEM stack_top_element;
 
-  if (scm_i_critical_section_level)
+  if (thread->critical_section_level)
     {
       fprintf (stderr, "continuation invoked from within critical section.\n");
       abort ();
diff --git a/libguile/threads.c b/libguile/threads.c
index 05e01e3f6..fc3e6076a 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -422,6 +422,7 @@ guilify_self_1 (SCM_STACKITEM *base)
   t->active_asyncs = SCM_EOL;
   t->block_asyncs = 1;
   t->pending_asyncs = 1;
+  t->critical_section_level = 0;
   t->last_debug_frame = NULL;
   t->base = base;
 #ifdef __ia64__
@@ -1667,7 +1668,6 @@ scm_i_thread_sleep_for_gc ()
 /* This mutex is used by SCM_CRITICAL_SECTION_START/END.
  */
 scm_i_pthread_mutex_t scm_i_critical_section_mutex;
-int scm_i_critical_section_level = 0;
 
 static SCM dynwind_critical_section_mutex;
 
diff --git a/libguile/threads.h b/libguile/threads.h
index 9417b88f1..2b0e06708 100644
--- a/libguile/threads.h
+++ b/libguile/threads.h
@@ -113,6 +113,9 @@ typedef struct scm_i_thread {
   scm_t_contregs *pending_rbs_continuation;
 #endif
 
+  /* Whether this thread is in a critical section. */
+  int critical_section_level;
+
 } scm_i_thread;
 
 #define SCM_I_IS_THREAD(x)    SCM_SMOB_PREDICATE (scm_tc16_thread, x)
diff --git a/libguile/throw.c b/libguile/throw.c
index 7e2803f3d..92c5a1aa5 100644
--- a/libguile/throw.c
+++ b/libguile/throw.c
@@ -692,7 +692,7 @@ scm_ithrow (SCM key, SCM args, int noreturn SCM_UNUSED)
   SCM dynpair = SCM_UNDEFINED;
   SCM winds;
 
-  if (scm_i_critical_section_level)
+  if (SCM_I_CURRENT_THREAD->critical_section_level)
     {
       fprintf (stderr, "throw from within critical section.\n");
       abort ();