diff --git a/mininet/clean.py b/mininet/clean.py
index f2e4375..b8f3ca5 100755
--- a/mininet/clean.py
+++ b/mininet/clean.py
@@ -51,7 +51,7 @@ class Cleanup( object ):
         info( "*** Removing excess controllers/ofprotocols/ofdatapaths/"
               "pings/noxes\n" )
         zombies = 'controller ofprotocol ofdatapath ping nox_core lt-nox_core '
-        zombies += 'ovs-openflowd ovs-controller udpbwtest mnexec ivs'
+        zombies += 'ovs-openflowd ovs-controller udpbwtest mnexec ivs ryu-manager'
         # Note: real zombie processes can't actually be killed, since they
         # are already (un)dead. Then again,
         # you can't connect to them either, so they're mostly harmless.