diff --git a/libmproxy/flow.py b/libmproxy/flow.py
index d9df7a1af..03b8b309c 100644
--- a/libmproxy/flow.py
+++ b/libmproxy/flow.py
@@ -168,8 +168,6 @@ class State:
         self.intercept = None
 
     def clientconnect(self, cc):
-        if not isinstance(cc, proxy.ClientConnect):
-            assert False
         self.client_connections.append(cc)
 
     def clientdisconnect(self, dc):
@@ -182,8 +180,6 @@ class State:
         """
             Add a request to the state. Returns the matching flow.
         """
-        if not isinstance(req, proxy.Request):
-            assert False
         f = Flow(req)
         self.flow_list.insert(0, f)
         self.flow_map[req] = f
@@ -193,8 +189,6 @@ class State:
         """
             Add a response to the state. Returns the matching flow.
         """
-        if not isinstance(resp, proxy.Response):
-            assert False
         f = self.flow_map.get(resp.request)
         if not f:
             return False
@@ -230,14 +224,6 @@ class State:
         else:
             return tuple(self.flow_list[:])
 
-    def get_client_conn(self, itm):
-        if isinstance(itm, proxy.ClientConnect):
-            return itm
-        elif hasattr(itm, "client_conn"):
-            return itm.client_conn
-        elif hasattr(itm, "request"):
-            return itm.request.client_conn
-
     def delete_flow(self, f):
         if not f.intercepting:
             if f.request in self.flow_map:
@@ -259,7 +245,6 @@ class State:
         self.delete_flow(f)
 
     def revert(self, f):
-        conn = self.get_client_conn(f)
         f.revert()
 
     def replay(self, f, masterq):
@@ -271,7 +256,6 @@ class State:
             return "Can't replay while intercepting..."
         if f.request:
             f.backup()
-            conn = self.get_client_conn(f)
             f.request.set_replay()
             if f.request.content:
                 f.request.headers["content-length"] = [str(len(f.request.content))]
@@ -297,15 +281,11 @@ class FlowMaster(controller.Master):
 
     def handle_error(self, r):
         f = self.state.add_error(r)
-        if not f:
-            r.ack()
+        r.ack()
         return f
 
     def handle_request(self, r):
-        f = self.state.add_request(r)
-        if not f:
-            r.ack()
-        return f
+        return self.state.add_request(r)
 
     def handle_response(self, r):
         f = self.state.add_response(r)
diff --git a/test/test_flow.py b/test/test_flow.py
index 3998943c3..eb6a7c8c0 100644
--- a/test/test_flow.py
+++ b/test/test_flow.py
@@ -26,6 +26,7 @@ class uFlow(libpry.AutoTree):
         f.response = utils.tresp()
         f.request = f.response.request
         assert not f.match(filt.parse("~b test"))
+        assert not f.match(None)
 
     def test_backup(self):
         f = utils.tflow()
@@ -41,8 +42,12 @@ class uFlow(libpry.AutoTree):
 
     def test_getset_state(self):
         f = utils.tflow()
-        f.response = utils.tresp()
-        f.request = f.response.request
+        f.response = utils.tresp(f.request)
+        state = f.get_state() 
+        assert f == flow.Flow.from_state(state)
+
+        f.response = None
+        f.error = proxy.Error(f, "error")
         state = f.get_state() 
         assert f == flow.Flow.from_state(state)
 
@@ -236,18 +241,29 @@ class uSerialize(libpry.AutoTree):
 
 
 class uFlowMaster(libpry.AutoTree):
-    def test_one(self):
+    def test_all(self):
         s = flow.State()
-        f = flow.FlowMaster(None, s)
+        fm = flow.FlowMaster(None, s)
         req = utils.treq()
 
-        f.handle_request(req)
+        fm.handle_clientconnect(req.client_conn)
+
+        f = fm.handle_request(req)
         assert len(s.flow_list) == 1
 
         resp = utils.tresp(req)
-        f.handle_response(resp)
+        fm.handle_response(resp)
         assert len(s.flow_list) == 1
+
+        rx = utils.tresp()
+        assert not fm.handle_response(rx)
         
+        dc = proxy.ClientDisconnect(req.client_conn)
+        fm.handle_clientdisconnect(dc)
+
+        err = proxy.Error(f, "msg")
+        fm.handle_error(err)
+
 
 
 tests = [