diff --git a/mosaic/libmosaic/__init__.py b/mosaic/libmosaic/__init__.py
index 10a5577..1c05fc8 100644
--- a/mosaic/libmosaic/__init__.py
+++ b/mosaic/libmosaic/__init__.py
@@ -3,3 +3,5 @@
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
+
+# pyre-strict