diff --git a/lib/fusion.c b/lib/fusion.c
index 201d5f6..d6562b4 100644
--- a/lib/fusion.c
+++ b/lib/fusion.c
@@ -45,10 +45,6 @@
 #include <tmmintrin.h>
 #include <nmmintrin.h>
 #include <wmmintrin.h>
-#ifdef _WINDOWS
-#include "wincompat.h"
-__m128i _mm_insert_epi64(__m128i a, __int64 i, const int imm8);
-#endif
 #include "picotls.h"
 #include "picotls/fusion.h"