diff --git a/src/map.c b/src/map.c
index 31742c1..2e792fe 100644
--- a/src/map.c
+++ b/src/map.c
@@ -1552,7 +1552,7 @@
 			escaped = vim_strsave_escape_csi(tb + j);
 			if (escaped != NULL)
 			{
-			    newlen = STRLEN(escaped);
+			    newlen = (int)STRLEN(escaped);
 			    mch_memmove(tb + j, escaped, newlen);
 			    j += newlen;
 			    vim_free(escaped);