diff --git a/karma.conf.js b/karma.conf.js
index db60ea5..19eac48 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -15,6 +15,8 @@ module.exports = function (config) {
             args: ['re_frame.test_runner.run_karma']
         },
 
+        autoWatchBatchDelay: 500,
+
         // the default configuration
         junitReporter: {
             outputDir: junitOutputDir + '/karma', // results will be saved as $outputDir/$browserName.xml
diff --git a/src/re_frame/subs.cljc b/src/re_frame/subs.cljc
index 6fc5a28..1f42c6f 100644
--- a/src/re_frame/subs.cljc
+++ b/src/re_frame/subs.cljc
@@ -102,9 +102,9 @@
          (when debug-enabled?
            (when-let [not-reactive (not-empty (remove ratom? dynv))]
              (console :warn "re-frame: your subscription's dynamic parameters that don't implement IReactiveAtom:" not-reactive)))
-         (when-not handler-fn
-           (trace/merge-trace! {:error true})
-           (console :error (str "re-frame: no subscription handler registered for: \"" query-id "\". Returning a nil subscription."))
+         (if (nil? handler-fn)
+           (do (trace/merge-trace! {:error true})
+               (console :error (str "re-frame: no subscription handler registered for: \"" query-id "\". Returning a nil subscription.")))
            (let [dyn-vals (make-reaction (fn [] (mapv deref dynv)))
                  sub      (make-reaction (fn [] (handler-fn app-db v @dyn-vals)))]
              ;; handler-fn returns a reaction which is then wrapped in the sub reaction
diff --git a/test/re-frame/subs_test.cljs b/test/re-frame/subs_test.cljs
index cbdd1bf..8850a9e 100644
--- a/test/re-frame/subs_test.cljs
+++ b/test/re-frame/subs_test.cljs
@@ -1,6 +1,6 @@
 (ns re-frame.subs-test
-  (:require [cljs.test         :as test :refer-macros [is deftest]]
-            [reagent.ratom     :refer-macros [reaction]]
+  (:require [cljs.test         :as test :refer-macros [is deftest testing]]
+            [reagent.ratom     :as r :refer-macros [reaction]]
             [re-frame.subs     :as subs]
             [re-frame.db       :as db]
             [re-frame.core     :as re-frame]))
@@ -268,3 +268,18 @@
         (fn [[a b] [_ c]] {:a a :b b})))
 
     (is (false? @sub-called?))))
+
+;; Dynamic subscriptions
+
+(deftest test-dynamic-subscriptions
+  (subs/reg-sub
+    :dyn-sub
+    (fn [db ev dynv]
+      (first dynv)))
+
+  (testing "happy case"
+    (is (= 1 @(subs/subscribe [:dyn-sub] [(r/atom 1)]))))
+  (testing "subscription that doesn't exist"
+    (is (nil? (subs/subscribe [:non-existent] [(r/atom 1)]))))
+  (testing "Passing a non-reactive value to a dynamic subscription"
+    (is (thrown-with-msg? js/Error #"No protocol method IDeref" @(subs/subscribe [:dyn-sub] [1])))))