diff --git a/library/rsa.c b/library/rsa.c
index ea88871..351f4af 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -45,6 +45,7 @@
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
 #include "constant_time.h"
+#include "mbedtls/constant_time.h"
 
 #include <string.h>