diff --git a/src/sm9_math.c b/src/sm9_math.c
index 40e685e2..be3856e2 100644
--- a/src/sm9_math.c
+++ b/src/sm9_math.c
@@ -52,6 +52,7 @@
 #include <stdlib.h>
 #include <assert.h>
 #include <gmssl/hex.h>
+#include <gmssl/sm9.h>
 #include "endian.h"