diff --git a/mod_http2/mod_proxy_http2.c b/mod_http2/mod_proxy_http2.c
index 2208707..844653e 100644
--- a/mod_http2/mod_proxy_http2.c
+++ b/mod_http2/mod_proxy_http2.c
@@ -159,6 +159,16 @@ static int proxy_http2_canon(request_rec *r, char *url)
             path = ap_proxy_canonenc(r->pool, url, (int)strlen(url),
                                      enc_path, 0, r->proxyreq);
             search = r->args;
+            if (search && *(ap_scan_vchar_obstext(search))) {
+                /*
+                 * We have a raw control character or a ' ' in r->args.
+                 * Correct encoding was missed.
+                 */
+                ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(10412)
+                              "To be forwarded query string contains control "
+                              "characters or spaces");
+                return HTTP_FORBIDDEN;
+            }
         }
         break;
     case PROXYREQ_PROXY: