diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 3ae6ddb28..a0c4ea3b8 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1688,7 +1688,7 @@ ngx_http_find_virtual_server(ngx_http_request_t *r, u_char *host, size_t len)
 
 #if (NGX_PCRE)
 
-    if (r->virtual_names->nregex) {
+    if (len && r->virtual_names->nregex) {
         size_t                   ncaptures;
         ngx_int_t                n;
         ngx_uint_t               i;