--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -300,25 +300,32 @@ class Build(MachCommandBase):
         * faster - builds JavaScript, XUL, CSS, etc files.
 
         "binaries" and "faster" almost fully complement each other. However,
         there are build actions not captured by either. If things don't appear to
         be rebuilding, perform a vanilla `mach build` to rebuild the world.
         """
         import which
         from mozbuild.controller.building import BuildMonitor
-        from mozbuild.util import resolve_target_to_make
+        from mozbuild.util import (
+            mkdir,
+            resolve_target_to_make,
+        )
 
         self.log_manager.register_structured_logger(logging.getLogger('mozbuild'))
 
         warnings_path = self._get_state_filename('warnings.json')
         monitor = self._spawn(BuildMonitor)
         monitor.init(warnings_path)
         ccache_start = monitor.ccache_stats()
 
+        # Disable indexing in objdir because it is not necessary and can slow
+        # down builds.
+        mkdir(self.topobjdir, not_indexed=True)
+
         with BuildOutputManager(self.log_manager, monitor) as output:
             monitor.start()
 
             if directory is not None and not what:
                 print('Can only use -C/--directory with an explicit target '
                     'name.')
                 return 1
 

--- a/python/mozbuild/mozbuild/util.py
+++ b/python/mozbuild/mozbuild/util.py
@@ -4,16 +4,17 @@
 
 # This file contains miscellaneous utility functions that don't belong anywhere
 # in particular.
 
 from __future__ import absolute_import, unicode_literals
 
 import argparse
 import collections
+import ctypes
 import difflib
 import errno
 import functools
 import hashlib
 import itertools
 import os
 import re
 import stat
@@ -31,16 +32,21 @@ from io import (
 )
 
 
 if sys.version_info[0] == 3:
     str_type = str
 else:
     str_type = basestring
 
+if sys.platform == 'win32':
+    _kernel32 = ctypes.windll.kernel32
+    _FILE_ATTRIBUTE_NOT_CONTENT_INDEXED = 0x2000
+
+
 def hash_file(path, hasher=None):
     """Hashes a file specified by the path given and returns the hex digest."""
 
     # If the default hashing function changes, this may invalidate
     # lots of cached data.  Don't change it lightly.
     h = hasher or hashlib.sha1()
 
     with open(path, 'rb') as fh:
@@ -106,16 +112,38 @@ def ensureParentDir(path):
     if d and not os.path.exists(path):
         try:
             os.makedirs(d)
         except OSError, error:
             if error.errno != errno.EEXIST:
                 raise
 
 
+def mkdir(path, not_indexed=False):
+    """Ensure a directory exists.
+
+    If ``not_indexed`` is True, an attribute is set that disables content
+    indexing on the directory.
+    """
+    try:
+        os.makedirs(path)
+    except OSError as e:
+        if e.errno != errno.EEXIST:
+            raise
+
+    if not_indexed:
+        if sys.platform == 'win32':
+            if isinstance(path, str_type):
+                fn = _kernel32.SetFileAttributesW
+            else:
+                fn = _kernel32.SetFileAttributesA
+
+            fn(path, _FILE_ATTRIBUTE_NOT_CONTENT_INDEXED)
+
+
 def simple_diff(filename, old_lines, new_lines):
     """Returns the diff between old_lines and new_lines, in unified diff form,
     as a list of lines.
 
     old_lines and new_lines are lists of non-newline terminated lines to
     compare.
     old_lines can be None, indicating a file creation.
     new_lines can be None, indicating a file deletion.