diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 2591742d4a..0bc5b8475e 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1183,7 +1183,9 @@ pub fn (c byte) is_letter() bool {
 }
 
 pub fn (s &string) free() {
-	if s.is_lit {return}
+	if s.is_lit || s.len == 0 {
+		return
+	}
 	free(s.str)
 }