diff --git a/include/remill/Arch/Runtime/Int.h b/include/remill/Arch/Runtime/Int.h
index 165c1f2a..66867c05 100644
--- a/include/remill/Arch/Runtime/Int.h
+++ b/include/remill/Arch/Runtime/Int.h
@@ -73,7 +73,7 @@ typedef __int128_t int128_t;
 #elif defined(__sparc__)
 typedef __uint128_t uint128_t;
 typedef __int128_t int128_t;
-#elif !__is_identifier(_ExtInt)
+#elif defined(__is_identifier) && __is_identifier(_ExtInt)
 typedef unsigned _ExtInt(128) uint128_t;
 typedef signed _ExtInt(128) int128_t;
 #else