diff --git a/_pytest/assertion/__init__.py b/_pytest/assertion/__init__.py
index 3da99c63c..09f82c776 100644
--- a/_pytest/assertion/__init__.py
+++ b/_pytest/assertion/__init__.py
@@ -76,8 +76,7 @@ def pytest_load_initial_conftests(early_config, parser, args):
 
     hook = None
     if mode == "rewrite":
-        hook = rewrite.AssertionRewritingHook()  # noqa
-        hook.set_config(early_config)
+        hook = rewrite.AssertionRewritingHook(early_config)  # noqa
         sys.meta_path.insert(0, hook)
 
     early_config._assertstate.hook = hook
diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index efddc8920..b85ca686c 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -44,7 +44,9 @@ else:
 class AssertionRewritingHook(object):
     """PEP302 Import hook which rewrites asserts."""
 
-    def __init__(self):
+    def __init__(self, config):
+        self.config = config
+        self.fnpats = config.getini("python_files")
         self.session = None
         self.modules = {}
         self._register_with_pkg_resources()
@@ -52,10 +54,6 @@ class AssertionRewritingHook(object):
     def set_session(self, session):
         self.session = session
 
-    def set_config(self, config):
-        self.config = config
-        self.fnpats = config.getini("python_files")
-
     def find_module(self, name, path=None):
         state = self.config._assertstate
         state.trace("find_module called for: %s" % name)