diff --git a/include/rapidjson/schema.h b/include/rapidjson/schema.h
index 02a6d0f..e28ddf7 100644
--- a/include/rapidjson/schema.h
+++ b/include/rapidjson/schema.h
@@ -1762,7 +1762,7 @@ struct TokenHelper {
 template <typename Stack>
 struct TokenHelper<Stack, char> {
     RAPIDJSON_FORCEINLINE static void AppendIndexToken(Stack& documentStack, SizeType index) {
-        if (sizeof(SizeType) == 4) {
+        RAPIDJSON_IF_CONSTEXPR (sizeof(SizeType) == 4) {
             char *buffer = documentStack.template Push<char>(1 + 10); // '/' + uint
             *buffer++ = '/';
             const char* end = internal::u32toa(index, buffer);