diff --git a/ikcp.h b/ikcp.h
index 5626693..42cee60 100644
--- a/ikcp.h
+++ b/ikcp.h
@@ -123,7 +123,7 @@ typedef unsigned long long IUINT64;
 #endif
 #endif
 
-#ifndef inline
+#if (!defined(__cplusplus)) && (!defined(inline))
 #define inline INLINE
 #endif