diff --git a/core/field.go b/core/field.go
index 6283ca7e..8ee4d502 100644
--- a/core/field.go
+++ b/core/field.go
@@ -13,7 +13,7 @@ import (
 
 var fieldNameRegex = regexp.MustCompile(`^\w+$`)
 
-const maxSafeJSONInt = 1<<53 - 1
+const maxSafeJSONInt int64 = 1<<53 - 1
 
 // Commonly used field names.
 const (