diff --git a/library/bignum.c b/library/bignum.c
index 846f5a3..b147a54 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -41,7 +41,7 @@
 #include "mbedtls/bn_mul.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
-#include "constant_time.h"
+#include "constant_time_internal.h"
 
 #include <string.h>