diff --git a/c_gen/c_code_gen.py b/c_gen/c_code_gen.py
index ff9a654..10668b7 100644
--- a/c_gen/c_code_gen.py
+++ b/c_gen/c_code_gen.py
@@ -739,7 +739,7 @@
 
 #define OF_MATCH_BYTES(length) (((length) + 7) & 0xfff8)
 
-#if __BYTE_ORDER == __ORDER_BIG_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 #define U16_NTOH(val) (val)
 #define U32_NTOH(val) (val)
 #define U64_NTOH(val) (val)