diff --git a/pushnotifier/exceptions.py b/pushnotifier/exceptions.py
index b394ee5..4945f9f 100644
--- a/pushnotifier/exceptions.py
+++ b/pushnotifier/exceptions.py
@@ -1,9 +1,32 @@
-MalformedRequestError = Exception('the request is malformed, i.e. missing content')
-DeviceNotFoundError = Exception('a device couldn\'t be found')
-UserNotFoundError = Exception('user couldn\'t be found (incorrect username/password)')
-IncorrectCredentialsError = Exception('credentials are incorrect')
-UnauthorizedError = Exception('package name or api key is incorrect')
-PayloadTooLargeError = Exception('your image is too big (> 5 MB)')
-UnsupportedMediaTypeError = Exception('you passed an invalid file type or the device(s) you tried to send this image to can\'t receive images')
+# define Python user-defined exceptions
+class MalformedRequestError(Exception):
+    "the request is malformed, i.e. missing content"
+    pass
 
-UnknownError = Exception('an unknown error occured! please contact the author of this module!')
+class DeviceNotFoundError(Exception):
+    "a device couldn't be found"
+    pass
+    
+class UserNotFoundError(Exception):
+    "user couldn't be found (incorrect username/password)"
+    pass
+    
+class IncorrectCredentialsError(Exception):
+    "credentials are incorrect"
+    pass
+
+class UnauthorizedError(Exception):
+    "package name or api key is incorrect"
+    pass
+    
+class PayloadTooLargeError(Exception):
+    "your image is too big (> 5 MB)"
+    pass
+    
+class UnsupportedMediaTypeError(Exception):
+    "you passed an invalid file type or the device(s) you tried to send this image to can\'t receive images)"
+    pass
+    
+class UnknownError(Exception):
+    "an unknown error occured! please contact the author of this module!"
+    pass
\ No newline at end of file