diff --git a/gclient_scm.py b/gclient_scm.py
index 439bc6b116..8236282af1 100644
--- a/gclient_scm.py
+++ b/gclient_scm.py
@@ -589,9 +589,10 @@ class GitWrapper(SCMWrapper):
               return
             else:
               self.Print('Input not recognized')
-        elif re.match("error: Your local changes to '.*' would be "
-                      "overwritten by merge.  Aborting.\nPlease, commit your "
-                      "changes or stash them before you can merge.\n",
+        elif re.match("error: Your local changes to (')?.*(')? would be "
+                      "overwritten by merge(.  Aborting)?[:.]\n(.*\n)?Please, "
+                      "commit your changes or stash them before you can "
+                      "merge.\n",
                       e.stderr):
           if not printed_path:
             self.Print('_____ %s%s' % (self.relpath, rev_str), timestamp=False)
@@ -997,7 +998,7 @@ class GitWrapper(SCMWrapper):
                                   % (self.relpath, rev_str))
     try:
       scm.GIT.Capture(['diff-index', '--cached', '--name-status', '-r',
-                       '--ignore-submodules', 'HEAD', '--'],
+                       '--ignore-submodules', '--exit-code', 'HEAD', '--'],
                        cwd=self.checkout_path)
     except subprocess2.CalledProcessError:
       raise gclient_utils.Error('\n____ %s%s\n'
diff --git a/tests/gclient_scm_test.py b/tests/gclient_scm_test.py
index 163cc07457..a14ae35ca0 100755
--- a/tests/gclient_scm_test.py
+++ b/tests/gclient_scm_test.py
@@ -919,6 +919,14 @@ from :3
       return return_value
     return AskForData
 
+  def getCurrentBranch(self):
+    # Returns name of current branch or HEAD for detached HEAD
+    branch = gclient_scm.scm.GIT.Capture(['rev-parse', '--abbrev-ref', 'HEAD'],
+                                          cwd=self.base_path)
+    if branch == 'HEAD':
+      return None
+    return branch
+
   def setUp(self):
     TestCaseUtils.setUp(self)
     unittest.TestCase.setUp(self)
@@ -1200,12 +1208,44 @@ class ManagedGitWrapperTestCase(BaseGitWrapperTestCase):
                  'Fix the conflict and run gclient again.\n'
                  'See \'man git-rebase\' for details.\n')
     self.assertRaisesError(exception, scm.update, options, (), [])
+    # The merge conflict creates a detached head with local changes, so another
+    # scm.update attempt should fail (in a different way) because of that (a
+    # rather roundabout way to test that condition).
     exception = ('\n____ . at refs/remotes/origin/master\n'
                  '\tYou have unstaged changes.\n'
                  '\tPlease commit, stash, or reset.\n')
     self.assertRaisesError(exception, scm.update, options, (), [])
     sys.stdout.close()
 
+  def testUpdateDetachedConflict(self):
+    # Detached head mode should refuse to update when there are local changes
+    # (staged or unstaged).
+    if not self.enabled:
+      return
+    options = self.Options()
+    scm = gclient_scm.CreateSCM(url=self.url, root_dir=self.root_dir,
+                                relpath=self.relpath)
+    scm._Run(['checkout', '-q', 'a7142dc9f0009350b96a11f372b6ea658592aa95'],
+             options)
+    # Make sure it checked out a detached HEAD
+    self.assertEquals(self.getCurrentBranch(), None)
+    file_path = join(self.base_path, 'b')
+    open(file_path, 'w').writelines('conflict\n')
+    # Unstaged
+    # TODO(all): Ick. Gclient should really have exception subclasses or
+    # something, so we can avoid this fragile exception message matching.
+    exception = ('\n____ . at refs/remotes/origin/master\n'
+                 '\tYou have unstaged changes.\n'
+                 '\tPlease commit, stash, or reset.\n')
+    self.assertRaisesError(exception, scm.update, options, (), [])
+    # Staged
+    scm._Run(['add', 'b'], options)
+    exception = ('\n____ . at refs/remotes/origin/master\n'
+                 '\tYour index contains uncommitted changes\n'
+                 '\tPlease commit, stash, or reset.\n')
+    self.assertRaisesError(exception, scm.update, options, (), [])
+    sys.stdout.close()
+
   def testRevinfo(self):
     if not self.enabled:
       return
@@ -1429,14 +1469,6 @@ class UnmanagedGitWrapperTestCase(BaseGitWrapperTestCase):
     # pylint: disable=E1101
     self.assertNotIn(expected, value)
 
-  def getCurrentBranch(self):
-    # Returns name of current branch or HEAD for detached HEAD
-    branch = gclient_scm.scm.GIT.Capture(['rev-parse', '--abbrev-ref', 'HEAD'],
-                                          cwd=self.base_path)
-    if branch == 'HEAD':
-      return None
-    return branch
-
   def testUpdateClone(self):
     if not self.enabled:
       return