diff --git a/libvirtaio.py b/libvirtaio.py
index 0f74209..bb76e35 100644
--- a/libvirtaio.py
+++ b/libvirtaio.py
@@ -317,9 +317,8 @@ class virEventAsyncIOImpl(object):
         This is a coroutine.
         '''
         self.log.debug('ff_callback(iden=%d, opaque=...)', iden)
-        ret = libvirt.virEventInvokeFreeCallback(opaque)
+        libvirt.virEventInvokeFreeCallback(opaque)
         self._pending_dec()
-        return ret
 
     @asyncio.coroutine
     def drain(self):