diff --git a/src/rss_thread_watch/feed_generator.clj b/src/rss_thread_watch/feed_generator.clj
index c5528c3..2094262 100644
--- a/src/rss_thread_watch/feed_generator.clj
+++ b/src/rss_thread_watch/feed_generator.clj
@@ -165,7 +165,7 @@
                            (response/redirect (get @conf/GLOBAL-CONFIG :homepage)))))
 
          ;; No querry specified - don't know what to search for
-         (when-not (prms "q")
+         (when-not (some f/known-filter-set (keys prms))
            (throw (ex-info "400" {:status 400
                                   :header {"Content-Type" "text/plain"}
                                   :body (str "400 You MUST specify query with one OR more'q=searchTerm' (or 'Q=SeARChteRm' for case sensitive) url parameter(s)\n\n\n"
diff --git a/src/rss_thread_watch/filters.clj b/src/rss_thread_watch/filters.clj
index 1573583..071da96 100644
--- a/src/rss_thread_watch/filters.clj
+++ b/src/rss_thread_watch/filters.clj
@@ -34,3 +34,5 @@
   {"Q" case-sensitive-filter
    "q" case-insensitive-filter})
 
+(def known-filter-set (set (keys known-filters)))
+