diff --git a/qubes/api/__init__.py b/qubes/api/__init__.py
index 22abcbbb..a9e81c22 100644
--- a/qubes/api/__init__.py
+++ b/qubes/api/__init__.py
@@ -168,7 +168,7 @@ class AbstractQubesAPI(object):
 
     def fire_event_for_permission(self, **kwargs):
         '''Fire an event on the source qube to check for permission'''
-        return self.src.fire_event_pre('mgmt-permission:{}'.format(self.method),
+        return self.src.fire_event_pre('mgmt-permission:' + self.method,
             dest=self.dest, arg=self.arg, **kwargs)
 
     def fire_event_for_filter(self, iterable, **kwargs):