diff --git a/include/path.h b/include/path.h
index 497dbe7f..25c57b2b 100644
--- a/include/path.h
+++ b/include/path.h
@@ -51,7 +51,7 @@
 #define	DIR_FIRST	1
 #define	DIR_LAST	6
 
-extern int dirindex[];
+extern signed char dirindex['z'-'a'+1];
 extern int diroff[][2];
 extern s_char dirch[];
 
diff --git a/src/lib/common/path.c b/src/lib/common/path.c
index 98d55b2b..b6e33e9c 100644
--- a/src/lib/common/path.c
+++ b/src/lib/common/path.c
@@ -307,8 +307,9 @@ bp_clear_cachepath(void)
 double
 pathcost(struct sctstr *start, s_char *path, int mob_type)
 {
-    register int o;
-    register int cx, cy;
+    unsigned i;
+    int o;
+    int cx, cy;
     double cost = 0.0;
     struct sctstr *sp;
     int sx, sy, offset;
@@ -321,7 +322,12 @@ pathcost(struct sctstr *start, s_char *path, int mob_type)
 	    path++;
 	    continue;
 	}
-	o = dirindex[(int)((*path) - 'a')];
+	i = *path - 'a';
+	if (CANT_HAPPEN(i >= sizeof(dirindex) / sizeof(*dirindex)))
+	    break;
+	o = dirindex[i];
+	if (CANT_HAPPEN(o) < 0)
+	    break;
 	cx += diroff[o][0];
 	cy += diroff[o][1];
 	sx = XNORM(cx);
diff --git a/src/lib/global/dir.c b/src/lib/global/dir.c
index 27807778..3c503242 100644
--- a/src/lib/global/dir.c
+++ b/src/lib/global/dir.c
@@ -55,8 +55,9 @@ int diroff[][2] = {
 
 /* this maps a character from a to z into the diroff mappings.  It
    keeps us from having to loop if we don't want to */
-int dirindex[] = { 0, 4, 0, 0, 0, 0, 5, 0, 0, 2, 0, 0, 8,
-    3, 0, 0, 0, 0, 0, 0, 1, 7, 0, 0, 6, 0
+signed char dirindex[] = {
+    -1, 4, -1, -1, -1, -1, 5, 0, -1, 2, -1, -1, 8,
+    3, -1, -1, -1, -1, -1, -1, 1, 7, -1, -1, 6, -1
 };
 
 /* must agree with dirch[] and DIR_ defines */