diff --git a/hyperwallet/tests/resources/private-jwkset1-invalid b/hyperwallet/tests/resources/private-jwkset1-invalid
new file mode 100644
index 0000000..c545551
--- /dev/null
+++ b/hyperwallet/tests/resources/private-jwkset1-invalid
@@ -0,0 +1 @@
+invalid jwkset
\ No newline at end of file
diff --git a/hyperwallet/tests/test_encryption.py b/hyperwallet/tests/test_encryption.py
index 0265a68..f87e50b 100644
--- a/hyperwallet/tests/test_encryption.py
+++ b/hyperwallet/tests/test_encryption.py
@@ -4,6 +4,7 @@
 import time
 import json
 import os.path
+import mock
 
 from jwcrypto import jwk, jws as cryptoJWS
 from jwcrypto.common import json_encode
@@ -177,6 +178,42 @@ def __getJwkKeySet(self, location):
             else:
                 raise HyperwalletException('Wrong JWK key set location path = ' + location)
 
+    def test_should_throw_exception_when_jwk_set_file_has_invalid_json_format(self):
+
+        localDir = os.path.abspath(os.path.dirname(__file__))
+        clientPath = os.path.join(localDir, 'resources', 'private-jwkset1-invalid')
+        hyperwalletPath = os.path.join(localDir, 'resources', 'public-jwkset1')
+        encryption = Encryption(clientPath, hyperwalletPath)
+
+        with self.assertRaises(HyperwalletException) as exc:
+            encryption.encrypt('testMessage')
+
+        self.assertEqual(exc.exception.message, 'Wrong JWK key set invalid jwkset')
+
+    @mock.patch('requests.Session.request')
+    def test_should_throw_exception_when_jwk_set_file_retrieved_from_url_is_invalid(self, session_mock):
+
+        data = {
+            'key': 'value'
+        }
+
+        session_mock.return_value = mock.MagicMock(
+            status_code=200,
+            content=data,
+            headers={
+                "Content-Type": "application/json"
+            }
+        )
+
+        localDir = os.path.abspath(os.path.dirname(__file__))
+        hyperwalletPath = os.path.join(localDir, 'resources', 'public-jwkset1')
+        encryption = Encryption('https://api.sandbox.hyperwallet.com/', hyperwalletPath)
+
+        with self.assertRaises(TypeError) as exc:
+            encryption.encrypt('testMessage')
+
+        self.assertEqual(exc.exception.message, 'expected string or buffer')
+
     def __findJwkKeyByAlgorithm(self, jwkKeySet, algorithm):
         '''
         Finds JWK key by given algorithm.
diff --git a/hyperwallet/utils/apiclient.py b/hyperwallet/utils/apiclient.py
index 4fcfcad..af0e9e9 100644
--- a/hyperwallet/utils/apiclient.py
+++ b/hyperwallet/utils/apiclient.py
@@ -203,8 +203,6 @@ def __checkResponseHeaderContentType(self, response):
             Response to be checked. **REQUIRED**
         '''
 
-        if response is None:
-            return
         contentType = response.headers['Content-Type']
         if (not self.encrypted and contentType != 'application/json') or (self.encrypted and contentType != 'application/jose+json'):
             raise HyperwalletAPIException('Invalid Content-Type specified in Response Header')
diff --git a/hyperwallet/utils/encryption.py b/hyperwallet/utils/encryption.py
index bb8515d..221203a 100644
--- a/hyperwallet/utils/encryption.py
+++ b/hyperwallet/utils/encryption.py
@@ -145,7 +145,7 @@ def __findJwkKeyByAlgorithm(self, jwkKeySet, algorithm):
         try:
             keySet = json.loads(jwkKeySet)
         except ValueError:
-            raise HyperwalletException('Wrong JWK key set' + jwkKeySet)
+            raise HyperwalletException('Wrong JWK key set ' + jwkKeySet)
 
         for key in keySet['keys']:
             if key['alg'] == algorithm: