diff --git a/python/mozbuild/mozbuild/frontend/context.py b/python/mozbuild/mozbuild/frontend/context.py
index 41ae8ae..dcc3263 100644
--- a/python/mozbuild/mozbuild/frontend/context.py
+++ b/python/mozbuild/mozbuild/frontend/context.py
@@ -408,8 +408,6 @@ class Path(ContextDerivedValue, unicode):
 class SourcePath(Path):
     """Like Path, but limited to paths in the source directory."""
     def __init__(self, context, value):
-        if value.startswith('!'):
-            raise ValueError('Object directory paths are not allowed')
         if value.startswith('%'):
             raise ValueError('Filesystem absolute paths are not allowed')
         super(SourcePath, self).__init__(context, value)