diff --git a/webapp2.py b/webapp2.py
index 96dc905..396182f 100755
--- a/webapp2.py
+++ b/webapp2.py
@@ -994,7 +994,7 @@ def _build(self, args, kwargs):
                 value = str(value)
 
             if not regex.match(value):
-                raise ValueError('URI buiding error: Value "%s" is not '
+                raise ValueError('URI building error: Value "%s" is not '
                     'supported for argument "%s".' % (value, name.strip('_')))
 
             values[name] = value