diff --git a/lib/doh.c b/lib/doh.c
index 05a6cc2357903a..196e89d93dfc23 100644
--- a/lib/doh.c
+++ b/lib/doh.c
@@ -264,6 +264,9 @@ static CURLcode dohprobe(struct Curl_easy *data,
 #ifndef CURLDEBUG
     /* enforce HTTPS if not debug */
     ERROR_CHECK_SETOPT(CURLOPT_PROTOCOLS, CURLPROTO_HTTPS);
+#else
+    /* in debug mode, also allow http */
+    ERROR_CHECK_SETOPT(CURLOPT_PROTOCOLS, CURLPROTO_HTTP|CURLPROTO_HTTPS);
 #endif
     ERROR_CHECK_SETOPT(CURLOPT_TIMEOUT_MS, (long)timeout_ms);
     if(data->set.verbose)