diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 771ba4fb75..69ae355aed 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1274,6 +1274,7 @@ fn (u &ustring) free() {
 	}
 	unsafe {
 		u.runes.free()
+		u.s.free()
 	}
 }