diff --git a/vlib/json/json_primitives.v b/vlib/json/json_primitives.v
index aade8e54c2..f46cfea747 100644
--- a/vlib/json/json_primitives.v
+++ b/vlib/json/json_primitives.v
@@ -28,6 +28,8 @@ fn C.cJSON_PrintUnformatted(&C.cJSON) &char
 
 fn C.cJSON_Print(&C.cJSON) &char
 
+fn C.cJSON_free(voidptr)
+
 pub fn decode(typ voidptr, s string) ?voidptr {
 	// compiler implementation
 	return 0
@@ -215,12 +217,16 @@ fn json_parse(s string) &C.cJSON {
 // json_string := json_print(encode_User(user))
 fn json_print(json &C.cJSON) string {
 	s := C.cJSON_PrintUnformatted(json)
-	return unsafe { tos(&u8(s), C.strlen(&char(s))) }
+	r := unsafe { tos_clone(&u8(s)) }
+	C.cJSON_free(s)
+	return r
 }
 
 fn json_print_pretty(json &C.cJSON) string {
 	s := C.cJSON_Print(json)
-	return unsafe { tos(&u8(s), C.strlen(&char(s))) }
+	r := unsafe { tos_clone(&u8(s)) }
+	C.cJSON_free(s)
+	return r
 }
 
 // /  cjson wrappers