diff --git a/saml_mapping_provider.py b/saml_mapping_provider.py
index f3f6f3d..82f0a0e 100644
--- a/saml_mapping_provider.py
+++ b/saml_mapping_provider.py
@@ -29,18 +29,19 @@ class SamlMappingProvider(object):
             ("[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),))
         )
         self._multiple_to_single_dot_pattern = re.compile(r"\.{2,}")
-
         self._string_end_dot_pattern = re.compile(r"\.$")
-        self._mxid_source_attribute = None
 
     def saml_response_to_user_attributes(
             self,
+            config: dict,
             saml_response: saml2.response.AuthnResponse,
             failures: int = 0,
     ) -> dict:
         """Maps some text from a SAML response to attributes of a new user
 
         Args:
+            config: A configuration dictionary
+
             saml_response: A SAML auth response object
 
             failures: How many times a call to this function with this
@@ -52,7 +53,7 @@ class SamlMappingProvider(object):
                 * displayname (str): The displayname of the user
         """
         # The calling function will catch the KeyError if this fails
-        mxid_source = saml_response.ava[self._mxid_source_attribute][0]
+        mxid_source = saml_response.ava[config["mxid_source_attribute"]][0]
 
         # Truncate the username to the first found '@' character to prevent complete
         # emails being leaked
@@ -94,8 +95,3 @@ class SamlMappingProvider(object):
         # Remove any trailing dots
         username = self._string_end_dot_pattern.sub("", username)
         return username
-
-    def parse_config(self, config):
-        """Parse the dict provided by the homeserver config"""
-        self._mxid_source_attribute = config.get("mxid_source_attribute", "uid")
-