diff -U4 -r guile-2.0.9/libguile/threads.c guile-2.0.9-new/libguile/threads.c
--- guile-2.0.9/libguile/threads.c	Mon Mar 18 23:30:13 2013
+++ guile-2.0.9-new/libguile/threads.c	Mon Jun 17 11:03:04 2013
@@ -325,12 +325,22 @@
   for (p = SCM_CDR (q); !scm_is_null (p); p = SCM_CDR (p))
     {
       if (scm_is_eq (p, c))
 	{
-	  if (scm_is_eq (c, SCM_CAR (q)))
-	    SCM_SETCAR (q, SCM_CDR (c));
+	  /* Remove c from the list */
 	  SCM_SETCDR (prev, SCM_CDR (c));
 
+	  /* If c is the last entry in the list,
+	     then update the (car q) to be the new last entry.
+	     Check whether the q is now empty. */
+	  if (scm_is_eq (c, SCM_CAR (q)))
+	    {
+	      if (scm_is_null (SCM_CDR (q)))
+		SCM_SETCAR (q, SCM_EOL);
+	      else
+		SCM_SETCAR (q, prev);
+	    }
+		
 	  /* GC-robust */
 	  SCM_SETCDR (c, SCM_EOL);
 
 	  SCM_CRITICAL_SECTION_END;