diff --git a/build_tools/marshal.py b/build_tools/marshal.py
index 4a1522f0b8..58c78e1632 100644
--- a/build_tools/marshal.py
+++ b/build_tools/marshal.py
@@ -50,6 +50,7 @@ this script, and to read in and execute the marshalled code later.
 
 import locale
 import marshal
+import os
 import sys
 import zlib