diff --git a/include/gmssl/sm9.h b/include/gmssl/sm9.h
index 7021b186..4839a2a3 100644
--- a/include/gmssl/sm9.h
+++ b/include/gmssl/sm9.h
@@ -46,6 +46,8 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <stdint.h>
+
 #ifndef GMSSL_SM9_H
 #define GMSSL_SM9_H