diff --git a/src/getchar.c b/src/getchar.c
index 0569372..fb28160 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -3922,7 +3922,7 @@
     if (mapchars != NULL)
     {
 	msg_puts(mapchars);
-	len = STRLEN(mapchars);
+	len = (int)STRLEN(mapchars);
 	vim_free(mapchars);
     }