diff --git a/tests/utils.cpp b/tests/utils.cpp
index 4b336b7..187cdf3 100644
--- a/tests/utils.cpp
+++ b/tests/utils.cpp
@@ -228,11 +228,11 @@
     "test-schema:int8": 8,
     "test-schema:int16": 300,
     "test-schema:int32": -300,
-    "test-schema:int64": -999999999999999,
+    "test-schema:int64": "-999999999999999",
     "test-schema:uint8": 8,
     "test-schema:uint16": 300,
     "test-schema:uint32": 300,
-    "test-schema:uint64": 999999999999999,
+    "test-schema:uint64": "999999999999999",
     "test-schema:boolean": true,
     "test-schema:string": "AHOJ",
     "test-schema:enum": "A",