diff --git a/tests/topotests/lib/topogen.py b/tests/topotests/lib/topogen.py
index 116dd9a41e..5c6e9af8ad 100644
--- a/tests/topotests/lib/topogen.py
+++ b/tests/topotests/lib/topogen.py
@@ -386,7 +386,7 @@ class Topogen(object):
 
         if errors != '':
             self.set_error(errors, 'router_error')
-            assert errors != '', errors
+            assert False, errors
             return True
         return False