diff --git a/library/bignum.c b/library/bignum.c
index 3643326..b7718e2 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -42,6 +42,7 @@
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
 
+#include <limits.h>
 #include <string.h>
 
 #if defined(MBEDTLS_PLATFORM_C)