diff --git a/src/microhttpd/digestauth.c b/src/microhttpd/digestauth.c
index eb824fe2..41a016df 100644
--- a/src/microhttpd/digestauth.c
+++ b/src/microhttpd/digestauth.c
@@ -1188,7 +1188,7 @@ calculate_add_nonce_with_retry (struct MHD_Connection *const connection,
 struct test_header_param
 {
   struct MHD_Connection *connection;
-  unsigned int num_headers;
+  size_t num_headers;
 };
 
 /**