diff --git a/src/terminal.c b/src/terminal.c
index 0a5ccbc..52f8105 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -4230,7 +4230,7 @@
 	return 1;
     }
     mch_memmove((char *)gap->ga_data + gap->ga_len, frag.str, frag.len);
-    gap->ga_len += frag.len;
+    gap->ga_len += (int)frag.len;
     if (!frag.final)
 	return 1;