diff --git a/mitmproxy/protocol/http2.py b/mitmproxy/protocol/http2.py
index 83ff71e40..4b57174bc 100644
--- a/mitmproxy/protocol/http2.py
+++ b/mitmproxy/protocol/http2.py
@@ -206,37 +206,46 @@ class Http2Layer(base.Layer):
             self.streams[event.pushed_stream_id].request_data_finished.set()
             self.streams[event.pushed_stream_id].start()
         elif isinstance(event, events.PriorityUpdated):
+            mapped_stream_id = event.stream_id
+            if mapped_stream_id in self.streams and self.streams[mapped_stream_id].server_stream_id:
+                # if the stream is already up and running and was sent to the server
+                # use the mapped server stream id to update priority information
+                mapped_stream_id = self.streams[mapped_stream_id].server_stream_id
+
             if eid in self.streams:
                 if self.streams[eid].handled_priority_event is event:
-                    # This event was already handled during stream creation
+                    # this event was already handled during stream creation
                     # HeadersFrame + Priority information as RequestReceived
                     return True
-                if eid in self.streams:
-                    self.streams[eid].priority_weight = event.weight
-                    self.streams[eid].priority_depends_on = event.depends_on
-                    self.streams[eid].priority_exclusive = event.exclusive
-
-            stream_id = event.stream_id
-            if stream_id in self.streams.keys() and self.streams[stream_id].server_stream_id:
-                stream_id = self.streams[stream_id].server_stream_id
-
-            depends_on = event.depends_on
-            if depends_on in self.streams.keys() and self.streams[depends_on].server_stream_id:
-                depends_on = self.streams[depends_on].server_stream_id
+                self.streams[eid].priority_weight = event.weight
+                self.streams[eid].priority_depends_on = event.depends_on
+                self.streams[eid].priority_exclusive = event.exclusive
 
             with self.server_conn.h2.lock:
                 self.server_conn.h2.prioritize(
-                    stream_id,
+                    mapped_stream_id,
                     weight=event.weight,
-                    depends_on=depends_on,
+                    depends_on=self._map_depends_on_stream_id(mapped_stream_id, event.depends_on),
                     exclusive=event.exclusive
                 )
                 self.server_conn.send(self.server_conn.h2.data_to_send())
         elif isinstance(event, events.TrailersReceived):
-            raise NotImplementedError()
+            raise NotImplementedError("TrailersReceived not implemented")
 
         return True
 
+    def _map_depends_on_stream_id(self, stream_id, depends_on):
+        mapped_depends_on = depends_on
+        if mapped_depends_on in self.streams and self.streams[mapped_depends_on].server_stream_id:
+            # if the depends-on-stream is already up and running and was sent to the server
+            # use the mapped server stream id to update priority information
+            mapped_depends_on = self.streams[mapped_depends_on].server_stream_id
+        if stream_id == mapped_depends_on:
+            # looks like one of the streams wasn't opened yet
+            # prevent self-dependent streams which result in ProtocolError
+            mapped_depends_on += 2
+        return mapped_depends_on
+
     def _cleanup_streams(self):
         death_time = time.time() - 10
         for stream_id in self.streams.keys():
@@ -412,8 +421,6 @@ class Http2SingleStreamLayer(http._HttpTransmissionLayer, basethread.BaseThread)
         headers.insert(0, ":path", message.path)
         headers.insert(0, ":method", message.method)
         headers.insert(0, ":scheme", message.scheme)
-        self.server_stream_id = self.server_conn.h2.get_next_available_stream_id()
-        self.server_to_client_stream_ids[self.server_stream_id] = self.client_stream_id
 
         try:
             self.server_conn.h2.safe_send_headers(
@@ -422,7 +429,7 @@ class Http2SingleStreamLayer(http._HttpTransmissionLayer, basethread.BaseThread)
                 headers,
                 end_stream=self.no_body,
                 priority_weight=self.priority_weight,
-                priority_depends_on=self.priority_depends_on,
+                priority_depends_on=self._map_depends_on_stream_id(self.server_stream_id, self.priority_depends_on),
                 priority_exclusive=self.priority_exclusive,
             )
         except Exception as e: