diff --git a/library/x509.c b/library/x509.c
index 2205400..55daf74 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -998,7 +998,7 @@
 {
 #if defined(MBEDTLS_CERTS_C) && defined(MBEDTLS_SHA1_C)
     int ret;
-    int flags;
+    uint32_t flags;
     mbedtls_x509_crt cacert;
     mbedtls_x509_crt clicert;