diff --git a/src/lisp/gencgc.c b/src/lisp/gencgc.c
index 9caae2d53929f02115a3cf6c89c0ba5809e1e845..f06b23b6f7d6ae269997fab15b16974f251e83d1 100644
--- a/src/lisp/gencgc.c
+++ b/src/lisp/gencgc.c
@@ -1194,8 +1194,8 @@ gc_alloc_new_region(int nbytes, int unboxed, struct alloc_region *alloc_region)
 	for (p = (int *) alloc_region->start_addr;
 	     p < (int *) alloc_region->end_addr; p++)
 	    if (*p != 0)
-		fprintf(stderr, "** new region not zero @ %lx\n",
-			(unsigned long) p);
+		fprintf(stderr, "** new region not zero @ %lx: %lx\n",
+			(unsigned long) p, *p);
     }
 
     /* Setup the pages. */