diff --git a/c/foreign.c b/c/foreign.c
index 9b9f11f2e8..5c1c2abb3d 100644
--- a/c/foreign.c
+++ b/c/foreign.c
@@ -85,7 +85,7 @@ static ptr bvstring(const char *s) {
 
 /* multiplier weights each character, h = n factors in the length */
 static iptr symhash(s) const char *s; {
-  iptr n, h;
+  uptr n, h;
 
   h = n = strlen(s);
   while (n--) h = h * multiplier + *s++;