diff --git a/presubmit_canned_checks.py b/presubmit_canned_checks.py
index 321858933..4b5227772 100644
--- a/presubmit_canned_checks.py
+++ b/presubmit_canned_checks.py
@@ -1645,6 +1645,8 @@ def CheckCIPDManifest(input_api, output_api, path=None, content=None):
     assert path is None, 'Cannot provide both "path" and "content".'
     cmd += ['-ensure-file=-']
     kwargs['stdin'] = content
+    if input_api.sys.version_info.major != 2:
+      kwargs['stdin'] = kwargs['stdin'].encode('utf-8')
     # quick and dirty parser to extract checked packages.
     packages = [
       l.split()[0] for l in (ll.strip() for ll in content.splitlines())
diff --git a/tests/presubmit_unittest.py b/tests/presubmit_unittest.py
index e083c6cc9..00a65bab8 100755
--- a/tests/presubmit_unittest.py
+++ b/tests/presubmit_unittest.py
@@ -3125,7 +3125,7 @@ the current line as well!
         input_api, presubmit.OutputApi, content='manifest_content')
     self.assertEqual(command.cmd,
         ['cipd', 'ensure-file-verify', '-log-level', 'debug', '-ensure-file=-'])
-    self.assertEqual(command.stdin, 'manifest_content')
+    self.assertEqual(command.stdin, b'manifest_content')
     self.assertEqual(command.kwargs, {
         'stdin': subprocess.PIPE,
         'stdout': subprocess.PIPE,
@@ -3151,7 +3151,7 @@ the current line as well!
         })
     self.assertEqual(command.cmd,
         ['cipd', 'ensure-file-verify', '-ensure-file=-'])
-    self.assertEqual(command.stdin, content)
+    self.assertEqual(command.stdin, content.encode())
     self.assertEqual(command.kwargs, {
         'stdin': subprocess.PIPE,
         'stdout': subprocess.PIPE,