diff --git a/src/lti/launch_params.py b/src/lti/launch_params.py
index 46290c3..5e87f1a 100644
--- a/src/lti/launch_params.py
+++ b/src/lti/launch_params.py
@@ -160,7 +160,7 @@ def __init__(self, *args, **kwargs):
 
         # now verify we only got valid launch params
         for k in self.keys():
-            if not valid_param(k):
+            if not self.valid_param(k):
                 raise InvalidLaunchParamError(k)
 
         # enforce some defaults
@@ -181,11 +181,14 @@ def _param_value(self, param):
         else:
             return self._params[param]
 
+    def valid_param(self, param):
+        return valid_param(param)
+
     def __len__(self):
         return len(self._params)
 
     def __getitem__(self, item):
-        if not valid_param(item):
+        if not self.valid_param(item):
             raise KeyError("{} is not a valid launch param".format(item))
         try:
             return self._param_value(item)
@@ -194,7 +197,7 @@ def __getitem__(self, item):
             raise KeyError(item)
 
     def __setitem__(self, key, value):
-        if not valid_param(key):
+        if not self.valid_param(key):
             raise InvalidLaunchParamError(key)
         if key in LAUNCH_PARAMS_IS_LIST:
             if isinstance(value, list):
diff --git a/src/lti/tool_provider.py b/src/lti/tool_provider.py
index 8956293..4eaf480 100644
--- a/src/lti/tool_provider.py
+++ b/src/lti/tool_provider.py
@@ -21,11 +21,12 @@ class ToolProvider(ToolBase):
     '''
     Implements the LTI Tool Provider.
     '''
+    launch_params_class = LaunchParams
 
     @classmethod
     def from_unpacked_request(cls, secret, params, url, headers):
 
-        launch_params = LaunchParams(params)
+        launch_params = cls.launch_params_class(params)
 
         if 'oauth_consumer_key' not in launch_params:
             raise InvalidLTIRequestError("oauth_consumer_key not found!")
diff --git a/tests/test_tool_provider.py b/tests/test_tool_provider.py
index 3485999..d7678bb 100644
--- a/tests/test_tool_provider.py
+++ b/tests/test_tool_provider.py
@@ -19,13 +19,21 @@ def create_tp(key=None, secret=None, lp=None, launch_url=None,
               launch_headers=None, tp_class=ToolProvider):
     key = key or generate_client_id()
     secret = secret or generate_token()
-    launch_params = LaunchParams()
+    launch_params = tp_class.launch_params_class()
     if lp is not None:
         launch_params.update(lp)
     launch_url = launch_url or "http://example.edu"
     launch_headers = launch_headers or {}
     return tp_class(key, secret, launch_params, launch_url, launch_headers)
 
+class CustomLaunchParams(LaunchParams):
+    def valid_param(self, param):
+        result  = super(CustomLaunchParams, self).valid_param(param)
+        return result or param in ['basiclti_submit', 'launch_url']
+
+class CustomToolProvider(ToolProvider):
+    launch_params_class = CustomLaunchParams
+
 class TestToolProvider(unittest.TestCase):
 
     def test_constructor(self):
@@ -215,6 +223,29 @@ def test_last_outcome_request(self):
         tp.outcome_requests = ['foo','bar']
         self.assertEqual(tp.last_outcome_request(), 'bar')
 
+    def test_custom_launch_params(self):
+        key = generate_client_id()
+        secret = generate_token()
+        lp = {
+            'lti_version': 'foo',
+            'lti_message_type': 'bar',
+            'resource_link_id': 123,
+            'launch_url': 'more_foo',
+            'basiclti_submit': 'more_bar'
+        }
+        launch_url = 'http://example.edu/foo/bar'
+        launch_headers = {'Content-Type': 'baz'}
+        tp = create_tp(key, secret, lp, launch_url, launch_headers, tp_class=CustomToolProvider)
+
+        with patch.object(SignatureOnlyEndpoint, 'validate_request') as mv:
+            mv.return_value = True, None  # Tuple of valid, request
+            self.assertTrue(tp.is_valid_request(Mock()))
+            call_url, call_method, call_params, call_headers = mv.call_args[0]
+            self.assertEqual(call_url, launch_url)
+            self.assertEqual(call_method, 'POST')
+            self.assertEqual(call_params, lp)
+            self.assertEqual(call_headers, launch_headers)
+
 # mock the django.shortcuts import to allow testing
 mock = Mock()
 mock.shortcuts.redirect.return_value = 'foo'