diff --git a/library/cipher.c b/library/cipher.c
index f38eb04..a0354d6 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -29,7 +29,7 @@
 #include "mbedtls/cipher_internal.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
-#include "constant_time.h"
+#include "mbedtls/constant_time.h"
 
 #include <stdlib.h>
 #include <string.h>