diff --git a/README.md b/README.md
index c20557a..77be6cf 100644
--- a/README.md
+++ b/README.md
@@ -86,6 +86,6 @@ A Clojure library for JSON Web Token(JWT) [draft-ietf-oauth-json-web-token-19](h
 
 ## License
 
-Copyright © 2014 [uochan](http://twitter.com/uochan)
+Copyright © 2015 [uochan](http://twitter.com/uochan)
 
 Distributed under the Eclipse Public License, the same as Clojure.
diff --git a/project.clj b/project.clj
index 279c004..3a8f3c0 100644
--- a/project.clj
+++ b/project.clj
@@ -1,4 +1,4 @@
-(defproject clj-jwt "0.0.11"
+(defproject clj-jwt "0.0.12"
   :description  "Clojure library for JSON Web Token(JWT)"
   :url          "https://github.com/liquidz/clj-jwt"
   :license      {:name "Eclipse Public License"
@@ -8,7 +8,7 @@
                  [org.clojure/data.codec "0.1.0"]
                  [org.bouncycastle/bcprov-jdk15 "1.46"]
                  [crypto-equality "1.0.0"]
-                 [clj-time "0.8.0"]]
+                 [clj-time "0.9.0"]]
 
   :profiles {:dev {:dependencies [[midje "1.6.3"  :exclusions [org.clojure/clojure]]]}}
   :plugins  [[lein-midje "3.1.3"]])
diff --git a/src/clj_jwt/key.clj b/src/clj_jwt/key.clj
index 3a2dd59..ce49b0b 100644
--- a/src/clj_jwt/key.clj
+++ b/src/clj_jwt/key.clj
@@ -38,7 +38,7 @@
 (defn public-key-from-string
   [key-str & [pass-phrase]]
   (with-open [r (StringReader. key-str)]
-    (let [res (pem->key r pass-phrase)]
+    (when-let [res (pem->key r pass-phrase)]
       (if (public-key? res)
         res
         (.getPublic res)))))
diff --git a/test/clj_jwt/key_test.clj b/test/clj_jwt/key_test.clj
index 04282eb..3eaa1f9 100644
--- a/test/clj_jwt/key_test.clj
+++ b/test/clj_jwt/key_test.clj
@@ -45,7 +45,9 @@
   (fact "rsa encrypted key with wrong pass phrase from string"
     (-> "test/files/rsa/3des.key" slurp (public-key-from-string "wrong pass phrase") type)
     => (throws org.bouncycastle.openssl.EncryptionException))
-  )
+
+  (fact "invalid key string"
+    (public-key-from-string "foobar") => nil))
 
 (facts "ecdsa public key"
   (fact "ecdsa public key"