diff --git a/gclient.py b/gclient.py
index 657c5aff3..2ded56ba3 100755
--- a/gclient.py
+++ b/gclient.py
@@ -1720,11 +1720,13 @@ def CMDfetch(parser, args):
 class Flattener(object):
   """Flattens a gclient solution."""
 
-  def __init__(self, client):
+  def __init__(self, client, pin_all_deps=False):
     """Constructor.
 
     Arguments:
       client (GClient): client to flatten
+      pin_all_deps (bool): whether to pin all deps, even if they're not pinned
+          in DEPS
     """
     self._client = client
 
@@ -1738,18 +1740,35 @@ class Flattener(object):
     self._pre_deps_hooks = []
     self._vars = {}
 
-    self._flatten()
+    self._flatten(pin_all_deps=pin_all_deps)
 
   @property
   def deps_string(self):
     assert self._deps_string is not None
     return self._deps_string
 
-  def _flatten(self):
-    """Runs the flattener. Saves resulting DEPS string."""
+  def _flatten(self, pin_all_deps=False):
+    """Runs the flattener. Saves resulting DEPS string.
+
+    Arguments:
+      pin_all_deps (bool): whether to pin all deps, even if they're not pinned
+          in DEPS
+    """
     for solution in self._client.dependencies:
       self._flatten_solution(solution)
 
+    if pin_all_deps:
+      for dep in self._deps.itervalues():
+        if dep.parsed_url is None:
+          continue
+        url, revision = gclient_utils.SplitUrlRevision(dep.parsed_url)
+        if revision and gclient_utils.IsGitSha(revision):
+          continue
+        scm = gclient_scm.CreateSCM(
+            dep.parsed_url, self._client.root_dir, dep.name, dep.outbuf)
+        dep._parsed_url = dep._url = '%s@%s' % (
+            url, scm.revinfo(self._client._options, [], None))
+
     self._deps_string = '\n'.join(
         _GNSettingsToLines(
             self._client.dependencies[0]._gn_args_file,
@@ -1825,6 +1844,10 @@ class Flattener(object):
 def CMDflatten(parser, args):
   """Flattens the solutions into a single DEPS file."""
   parser.add_option('--output-deps', help='Path to the output DEPS file')
+  parser.add_option(
+      '--pin-all-deps', action='store_true',
+      help=('Pin all deps, even if not pinned in DEPS. CAVEAT: only does so '
+            'for checked out deps, NOT deps_os.'))
   options, args = parser.parse_args(args)
 
   options.nohooks = True
@@ -1836,7 +1859,7 @@ def CMDflatten(parser, args):
   if code != 0:
     return code
 
-  flattener = Flattener(client)
+  flattener = Flattener(client, pin_all_deps=options.pin_all_deps)
 
   if options.output_deps:
     with open(options.output_deps, 'w') as f:
diff --git a/tests/gclient_smoketest.py b/tests/gclient_smoketest.py
index 89fd9bb8c..ab993a4e3 100755
--- a/tests/gclient_smoketest.py
+++ b/tests/gclient_smoketest.py
@@ -704,6 +704,142 @@ class GClientSmokeGIT(GClientSmokeBase):
         '',
     ], deps_contents.splitlines())
 
+  def testFlattenPinAllDeps(self):
+    if not self.enabled:
+      return
+
+    output_deps = os.path.join(self.root_dir, 'DEPS.flattened')
+    self.assertFalse(os.path.exists(output_deps))
+
+    self.gclient(['config', self.git_base + 'repo_6', '--name', 'src'])
+    self.gclient(['sync'])
+    self.gclient(['flatten', '-v', '-v', '-v', '--output-deps', output_deps,
+                  '--pin-all-deps'])
+
+    with open(output_deps) as f:
+      deps_contents = f.read()
+
+    self.assertEqual([
+        'gclient_gn_args_file = "src/gclient.args"',
+        'gclient_gn_args = [\'DummyVariable\']',
+        'allowed_hosts = [',
+        '  "git://127.0.0.1:20000/git/",',
+        ']',
+        '',
+        'deps = {',
+        '  # src -> src/repo2 -> foo/bar',
+        '  "foo/bar": {',
+        '    "url": "/repo_3",',
+        '  },',
+        '',
+        '  # src',
+        '  "src": {',
+        '    "url": "git://127.0.0.1:20000/git/repo_6@%s",' % (
+                 self.githash('repo_6', 1)),
+        '  },',
+        '',
+        '  # src -> src/repo2',
+        '  "src/repo2": {',
+        '    "url": "git://127.0.0.1:20000/git/repo_2@%s",' % (
+                 self.githash('repo_2', 1)[:7]),
+        '    "condition": "True",',
+        '  },',
+        '',
+        '  # src -> src/repo4',
+        '  "src/repo4": {',
+        '    "url": "/repo_4",',
+        '    "condition": "False",',
+        '  },',
+        '',
+        '  # src -> src/repo8',
+        '  "src/repo8": {',
+        '    "url": "/repo_8",',
+        '  },',
+        '',
+        '}',
+        '',
+        'deps_os = {',
+        '  "mac": {',
+        '    # src -> src/mac_repo',
+        '    "src/mac_repo": {',
+        '      "url": "/repo_5",',
+        '    },',
+        '',
+        '    # src -> src/repo8 -> src/recursed_os_repo',
+        '    "src/recursed_os_repo": {',
+        '      "url": "/repo_5",',
+        '    },',
+        '',
+        '  },',
+        '',
+        '  "unix": {',
+        '    # src -> src/repo8 -> src/recursed_os_repo',
+        '    "src/recursed_os_repo": {',
+        '      "url": "/repo_5",',
+        '    },',
+        '',
+        '    # src -> src/unix_repo',
+        '    "src/unix_repo": {',
+        '      "url": "/repo_5",',
+        '    },',
+        '',
+        '  },',
+        '',
+        '  "win": {',
+        '    # src -> src/win_repo',
+        '    "src/win_repo": {',
+        '      "url": "/repo_5",',
+        '    },',
+        '',
+        '  },',
+        '',
+        '}',
+        '',
+        'hooks = [',
+        '  # src',
+        '  {',
+        '    "pattern": ".",',
+        '    "cwd": ".",',
+        '    "action": [',
+        '        "python",',
+        '        "-c",',
+        '        "open(\'src/git_hooked1\', \'w\').write(\'git_hooked1\')",',
+        '    ]',
+        '  },',
+        '',
+        '  # src',
+        '  {',
+        '    "pattern": "nonexistent",',
+        '    "cwd": ".",',
+        '    "action": [',
+        '        "python",',
+        '        "-c",',
+        '        "open(\'src/git_hooked2\', \'w\').write(\'git_hooked2\')",',
+        '    ]',
+        '  },',
+        '',
+        ']',
+        '',
+        'hooks_os = {',
+        '  "mac": [',
+        '    # src',
+        '    {',
+        '      "pattern": ".",',
+        '      "cwd": ".",',
+        '      "action": [',
+        '          "python",',
+        '          "-c",',
+        '          "open(\'src/git_hooked_mac\', \'w\').write('
+                             '\'git_hooked_mac\')",',
+        '      ]',
+        '    },',
+        '',
+        '  ],',
+        '',
+        '}',
+        '',
+    ], deps_contents.splitlines())
+
 
 class GClientSmokeGITMutates(GClientSmokeBase):
   """testRevertAndStatus mutates the git repo so move it to its own suite."""