diff --git a/mininet/net.py b/mininet/net.py
index d7bbf4f..29d3876 100755
--- a/mininet/net.py
+++ b/mininet/net.py
@@ -549,7 +549,8 @@ class Mininet( object ):
             switch.start( self.controllers )
         started = {}
         for swclass, switches in groupby(
-                sorted( self.switches, key=type ), type ):
+                sorted( self.switches,
+                        key=lambda s: str( type( s ) ) ), type ):
             switches = tuple( switches )
             if hasattr( swclass, 'batchStartup' ):
                 success = swclass.batchStartup( switches )
@@ -576,7 +577,8 @@ class Mininet( object ):
         info( '*** Stopping %i switches\n' % len( self.switches ) )
         stopped = {}
         for swclass, switches in groupby(
-                sorted( self.switches, key=type ), type ):
+                sorted( self.switches,
+                        key=lambda s: str( type( s ) ) ), type ):
             switches = tuple( switches )
             if hasattr( swclass, 'batchShutdown' ):
                 success = swclass.batchShutdown( switches )