diff --git a/modules/reitit-middleware/.nrepl-port b/modules/reitit-middleware/.nrepl-port
new file mode 100644
index 00000000..d0d8aacb
--- /dev/null
+++ b/modules/reitit-middleware/.nrepl-port
@@ -0,0 +1 @@
+43803
\ No newline at end of file
diff --git a/modules/reitit-middleware/src/reitit/ring/middleware/session.clj b/modules/reitit-middleware/src/reitit/ring/middleware/session.clj
index e90963e1..e0300204 100644
--- a/modules/reitit-middleware/src/reitit/ring/middleware/session.clj
+++ b/modules/reitit-middleware/src/reitit/ring/middleware/session.clj
@@ -2,15 +2,21 @@
   (:require
    [clojure.spec.alpha :as s]
    [ring.middleware.session :as session]
+   [ring.middleware.session.store :as session-store]
    [ring.middleware.session.memory :as memory]))
 
+(s/def ::store #(satisfies? session-store/SessionStore %))
+(s/def ::root string?)
+(s/def ::cookie-name string?)
+(s/def ::cookie-attrs map?)
+(s/def ::session (s/keys :opt-un [::store ::root ::cookie-name ::cookie-attrs]))
 (s/def ::spec (s/keys :opt-un [::session]))
 
 (def ^:private store
   "The default shared in-memory session store.
 
-  This is used when no `:session` key is provided to the middleware."
-  (atom {}))
+  This is used when no `:store` key is provided to the middleware."
+  (memory/memory-store (atom {})))
 
 (def session-middleware
   "Middleware for session.
@@ -25,9 +31,9 @@
 
   | key          | description |
   | -------------|-------------|
-  | `:session`   | `ring.middleware.session.store/SessionStore` instance. Use `ring.middleware.session.memory/MemoryStore` by default."
+  | `:session`   | A map of options that passes into the [`ring.middleware.session/wrap-session](http://ring-clojure.github.io/ring/ring.middleware.session.html#var-wrap-session) function`."
   {:name    :session
    :spec    ::spec
-   :compile (fn [{:keys [session]
-                 :or   {session {:store (memory/memory-store store)}}} _]
-              {:wrap #(session/wrap-session % session)})})
+   :compile (fn [{session-opts :session} _]
+              (let [session-opts (merge {:store store} session-opts)]
+                {:wrap #(session/wrap-session % session-opts)}))})
diff --git a/test/clj/reitit/ring/middleware/session_test.clj b/test/clj/reitit/ring/middleware/session_test.clj
index ca4acfe7..efaf41f7 100644
--- a/test/clj/reitit/ring/middleware/session_test.clj
+++ b/test/clj/reitit/ring/middleware/session_test.clj
@@ -2,7 +2,9 @@
   (:require [clojure.test :refer [deftest testing is]]
             [reitit.ring.middleware.session :as session]
             [ring.middleware.session.memory :as memory]
-            [reitit.ring :as ring]))
+            [reitit.spec :as rs]
+            [reitit.ring :as ring]
+            [reitit.ring.spec :as rrs]))
 
 (defn get-session-id
   "Parse the session-id out of response headers."
@@ -24,37 +26,54 @@
      :session {:counter counter}}))
 
 (deftest session-test
-  (let [store           (atom {})
-        app             (ring/ring-handler
-                         (ring/router
-                          ["/api"
-                           {:session    {:store (memory/memory-store store)}
-                            :middleware [session/session-middleware]}
-                           ["/ping" handler]
-                           ["/pong" handler]]))
-        first-response  (app {:request-method :get
-                              :uri            "/api/ping"})
-        session-id      (get-session-id first-response)
-        second-response (app {:request-method :get
-                              :uri            "/api/pong"
-                              :cookies        {"ring-session" {:value session-id}}})]
-    (is (= (count @store)
-           1))
-    (is (-> @store first second)
-        {:counter 2})))
+  (testing "Custom session store"
+    (let [store           (atom {})
+          app             (ring/ring-handler
+                           (ring/router
+                            ["/api"
+                             {:session    {:store (memory/memory-store store)}
+                              :middleware [session/session-middleware]}
+                             ["/ping" handler]
+                             ["/pong" handler]]))
+          first-response  (app {:request-method :get
+                                :uri            "/api/ping"})
+          session-id      (get-session-id first-response)
+          second-response (app {:request-method :get
+                                :uri            "/api/pong"
+                                :cookies        {"ring-session" {:value session-id}}})]
+      (testing "shared across routes"
+        (is (= (count @store)
+               1))
+        (is (-> @store first second)
+            {:counter 2})))))
 
 (deftest default-session-test
-  (let [app             (ring/ring-handler
-                         (ring/router
-                          ["/api"
-                           {:middleware [session/session-middleware]}
-                           ["/ping" handler]
-                           ["/pong" handler]]))
-        first-response  (app {:request-method :get
-                              :uri            "/api/ping"})
-        session-id      (get-session-id first-response)
-        second-response (app {:request-method :get
-                              :uri            "/api/pong"
-                              :cookies        {"ring-session" {:value session-id}}})]
-    (is (= (inc (get-in first-response [:body :counter]))
-           (get-in second-response [:body :counter])))))
+  (testing "Default session store"
+    (let [app             (ring/ring-handler
+                           (ring/router
+                            ["/api"
+                             {:middleware [session/session-middleware]}
+                             ["/ping" handler]
+                             ["/pong" handler]]))
+          first-response  (app {:request-method :get
+                                :uri            "/api/ping"})
+          session-id      (get-session-id first-response)
+          second-response (app {:request-method :get
+                                :uri            "/api/pong"
+                                :cookies        {"ring-session" {:value session-id}}})]
+      (testing "shared across routes"
+        (is (= (inc (get-in first-response [:body :counter]))
+               (get-in second-response [:body :counter])))))))
+
+(deftest session-spec-test
+  (testing "Session spec"
+    (testing "with invalid session store type"
+      (is
+       (thrown? Exception
+                (ring/ring-handler
+                 (ring/router
+                  ["/api"
+                   {:session    {:store nil}
+                    :middleware [session/session-middleware]
+                    :handler    handler}]
+                  {:validate rrs/validate})))))))