Index: /trunk/source/lisp-kernel/gc-common.c
===================================================================
--- /trunk/source/lisp-kernel/gc-common.c	(revision 14421)
+++ /trunk/source/lisp-kernel/gc-common.c	(revision 14422)
@@ -1138,5 +1138,7 @@
         memo_dnode += remain;
         p += (remain+remain);
-        bits = *++bitsp;
+        if (memo_dnode < num_memo_dnodes) {
+          bits = *++bitsp;
+        }
         bitidx = 0;
       } else {
@@ -1338,5 +1340,7 @@
           *bitsp = outbits;
         }
-        bits = *++bitsp;
+        if (memo_dnode < num_memo_dnodes) {
+          bits = *++bitsp;
+        }
         inbits = outbits = bits;
         bitidx = 0;