diff --git a/library/constant_time.c b/library/constant_time.c
index 5bd74b6..aff30ea 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -24,6 +24,7 @@
 
 #include "common.h"
 #include "constant_time.h"
+#include "mbedtls/constant_time.h"
 #include "mbedtls/error.h"
 #include "mbedtls/platform_util.h"