Index: src/pmc/hash.pmc
===================================================================
--- src/pmc/hash.pmc	(revision 34006)
+++ src/pmc/hash.pmc	(working copy)
@@ -1096,6 +1096,30 @@
             hash->entries   = elems;
         }
     }
+
+    METHOD sanity_check() {
+        Hash *hash = (Hash*)PMC_struct_val(SELF);
+        UINTVAL     i, j;
+
+        for (i = 0; i <= hash->mask; i++) {
+            HashBucket * const b      = hash->bs + i;
+            void       * const key    = b->key;
+            void       * const val    = b->value;
+
+            for (j = 0; j <= hash->mask; j++)
+                if (b == hash->bi[j])
+                    printf("index #%d maps to bucket #%d\n", j, i);
+
+            if (key)
+                printf("hash->bs+%d: '%s' => ", i, ((STRING*)key)->strstart);
+            if (val)
+                printf("'%s'\n", VTABLE_get_string(INTERP, (PMC*)val)->strstart );
+            if (key && !val)
+                printf(" (null)\n");
+            if (!key && !val)
+                printf("hash->bs+%d: key and value are null\n", i);
+        }
+    }
 }
 
 /*