diff --git a/pre-upload_unittest.py b/pre-upload_unittest.py
index 640aef8..88d665b 100755
--- a/pre-upload_unittest.py
+++ b/pre-upload_unittest.py
@@ -1632,7 +1632,9 @@
   def testBadRustFile(self):
     self.PatchObject(pre_upload, '_get_affected_files', return_value=['a.rs'])
     # Bad because it's missing trailing newline.
-    self.content_mock.return_value = 'fn main() {}'
+    content = 'fn main() {}'
+    self.content_mock.return_value = content
+    self.PatchObject(pre_upload, '_run_command', return_value=content + '\n')
     failure = pre_upload._check_rustfmt(ProjectNamed('PROJECT'), 'COMMIT')
     self.assertIsNotNone(failure)
     self.assertEquals('Files not formatted with rustfmt: '
@@ -1642,7 +1644,9 @@
 
   def testGoodRustFile(self):
     self.PatchObject(pre_upload, '_get_affected_files', return_value=['a.rs'])
-    self.content_mock.return_value = 'fn main() {}\n'
+    content = 'fn main() {}\n'
+    self.content_mock.return_value = content
+    self.PatchObject(pre_upload, '_run_command', return_value=content)
     failure = pre_upload._check_rustfmt(ProjectNamed('PROJECT'), 'COMMIT')
     self.assertIsNone(failure)