diff --git a/src/ChangeLog b/src/ChangeLog
index 0b03069c8d7..ea32a480a6c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2014-04-08  Daniel Colascione  <dancol@dancol.org>
 
+	* alloc.c (sweep_symbols, mark_object): Assert that symbol
+	function cells contain valid lisp objects.  (Modified version of
+	patch from Dmitry).
+
 	* alloc.c (detect_suspicious_free): Split actual stack capturing
 	out into new function for easier breakpoint setting.
 	(note_suspicious_free): New function.
diff --git a/src/alloc.c b/src/alloc.c
index d22e71bd1a8..15bfbbbb1b7 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6220,6 +6220,8 @@ mark_object (Lisp_Object arg)
 	  break;
 	CHECK_ALLOCATED_AND_LIVE (live_symbol_p);
 	ptr->gcmarkbit = 1;
+	/* Attempt to catch bogus objects.  */
+        eassert (valid_lisp_object_p (ptr->function) >= 1);
 	mark_object (ptr->function);
 	mark_object (ptr->plist);
 	switch (ptr->redirect)
@@ -6640,6 +6642,8 @@ sweep_symbols (void)
             {
               ++num_used;
               sym->s.gcmarkbit = 0;
+              /* Attempt to catch bogus objects.  */
+              eassert (valid_lisp_object_p (sym->s.function) >= 1);
             }
         }