diff --git a/src/openvpn/tls_crypt.c b/src/openvpn/tls_crypt.c
index 318c939..9026cff 100644
--- a/src/openvpn/tls_crypt.c
+++ b/src/openvpn/tls_crypt.c
@@ -539,7 +539,7 @@
     int64_t timestamp;
     memcpy(&timestamp, metadata + 1, sizeof(int64_t));
     timestamp = (int64_t)ntohll((uint64_t)timestamp);
-    int64_t max_age_in_seconds = max_days * 24 * 60 * 60;
+    int64_t max_age_in_seconds = (int64_t)max_days * 24 * 60 * 60;
     if (now - timestamp > max_age_in_seconds)
     {
         msg(M_WARN, "ERROR: Client key is too old.");