diff --git a/tools/android_illegal_imports.py b/tools/android_illegal_imports.py
index 2a2d5ac1fbf1f..e07573f141f92 100644
--- a/tools/android_illegal_imports.py
+++ b/tools/android_illegal_imports.py
@@ -17,7 +17,7 @@ def main():
   parser.add_argument('--files', type=str, required=True, nargs='+')
   args = parser.parse_args()
 
-  open(args.stamp, 'wa').close()
+  open(args.stamp, 'a').close()
 
   bad_files = []