diff --git a/pyramid/config.py b/pyramid/config.py
index 917b689b1b..60d406a62b 100644
--- a/pyramid/config.py
+++ b/pyramid/config.py
@@ -995,10 +995,10 @@ def _add_tween(self, tween_factory, alias=None, under=None, over=None,
             raise ConfigurationError('%s is a reserved tween name' % alias)
 
         if over is INGRESS:
-            raise ConfigurationError('%s cannot be over INGRESS')
+            raise ConfigurationError('%s cannot be over INGRESS' % name)
 
         if under is MAIN:
-            raise ConfigurationError('%s cannot be under MAIN')
+            raise ConfigurationError('%s cannot be under MAIN' % name)
 
         registry = self.registry
         tweens = registry.queryUtility(ITweens)