diff --git a/src/lib/commands/look.c b/src/lib/commands/look.c
index 493d7826..fffd99b5 100644
--- a/src/lib/commands/look.c
+++ b/src/lib/commands/look.c
@@ -70,7 +70,7 @@ do_look(int type)
 
     if (!snxtitem(&ni, type, player->argp[1], NULL))
 	return RET_SYN;
-    bitmap = calloc(WORLD_SZ() / 8, 1);
+    bitmap = calloc((WORLD_SZ() + 7) / 8, 1);
     if (!bitmap) {
 	logerror("malloc failed in do_look\n");
 	pr("Memory error.  Tell the deity.\n");
diff --git a/src/lib/commands/spy.c b/src/lib/commands/spy.c
index 72918606..b746b3d6 100644
--- a/src/lib/commands/spy.c
+++ b/src/lib/commands/spy.c
@@ -30,7 +30,7 @@
  *  Known contributors to this file:
  *     Dave Pare, 1986
  *     Steve McClure, 1998-2000
- *     Markus Armbruster, 2005-2008
+ *     Markus Armbruster, 2005-2011
  */
 
 #include <config.h>
@@ -86,7 +86,7 @@ spy(void)
 	pr("You don't have the BTU's for spying on that scale!\n");
 	return RET_FAIL;
     }
-    bitmap = calloc(WORLD_SZ() / 8, 1);
+    bitmap = calloc((WORLD_SZ() + 7) / 8, 1);
     if (!bitmap) {
 	logerror("malloc failed in do_look\n");
 	pr("Memory error.  Tell the deity.\n");
diff --git a/src/lib/subs/maps.c b/src/lib/subs/maps.c
index e2c4d890..14e89464 100644
--- a/src/lib/subs/maps.c
+++ b/src/lib/subs/maps.c
@@ -30,7 +30,7 @@
  *  Known contributors to this file:
  *     Ken Stevens, 1995
  *     Steve McClure, 1998
- *     Markus Armbruster, 2004-2008
+ *     Markus Armbruster, 2004-2011
  *     Ron Koenderink, 2006
  */
 
@@ -148,7 +148,7 @@ draw_map(int bmap, char origin, int map_flags, struct nstr_sect *nsp)
 	}
     }
     if (!bitmap)
-	bitmap = malloc(WORLD_SZ() / 8);
+	bitmap = malloc((WORLD_SZ() + 7) / 8);
     if (!wmapbuf || !wmap || !bitmap) {
 	pr("Memory error, tell the deity.\n");
 	logerror("malloc failed in draw_map\n");
@@ -202,7 +202,7 @@ draw_map(int bmap, char origin, int map_flags, struct nstr_sect *nsp)
 		struct sctstr sect;
 
 		if (!player->god) {
-		    memset(bitmap, 0, WORLD_SZ() / 8);
+		    memset(bitmap, 0, (WORLD_SZ() + 7) / 8);
 		    bitinit2(nsp, bitmap, player->cnum);
 		}
 		while (nxtsct(nsp, &sect) && !player->aborted) {
@@ -221,7 +221,7 @@ draw_map(int bmap, char origin, int map_flags, struct nstr_sect *nsp)
 	int changed = 0;
 
 	if (!player->god) {
-	    memset(bitmap, 0, WORLD_SZ() / 8);
+	    memset(bitmap, 0, (WORLD_SZ() + 7) / 8);
 	    bitinit2(nsp, bitmap, player->cnum);
 	}
 	while (nxtsct(nsp, &sect) && !player->aborted) {