diff --git a/src/highlight.c b/src/highlight.c
index 54e348d..9aa149f 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -860,7 +860,7 @@
 highlight_set_termgui_attr(int idx, char_u *key, char_u *arg, int init)
 {
     int		attr;
-    int		off;
+    size_t	off;
     keyvalue_T	target;
     keyvalue_T	*entry;