diff --git a/webrtc/base/base.gyp b/webrtc/base/base.gyp
index 23d8ffe165..4152448048 100644
--- a/webrtc/base/base.gyp
+++ b/webrtc/base/base.gyp
@@ -22,13 +22,12 @@
         }],
       ],
     }],
-    # TODO(tkchin): Mac support. There are a bunch of problems right now because
-    # of some settings pulled down from Chromium.
-    ['OS=="ios"', {
+    ['OS=="ios" or (OS=="mac" and mac_deployment_target=="10.7")', {
       'targets': [
         {
           'target_name': 'rtc_base_objc',
           'type': 'static_library',
+          'includes': [ '../build/objc_common.gypi' ],
           'dependencies': [
             'rtc_base',
           ],
@@ -60,10 +59,6 @@
               },
             }],
           ],
-          'xcode_settings': {
-            'CLANG_ENABLE_OBJC_ARC': 'YES',
-            'CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS': 'YES',
-          },
         }
       ],
     }], # OS=="ios"
diff --git a/webrtc/build/WebRTC-Prefix.pch b/webrtc/build/WebRTC-Prefix.pch
new file mode 100644
index 0000000000..ab1bc7a20d
--- /dev/null
+++ b/webrtc/build/WebRTC-Prefix.pch
@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+#if !defined(__has_feature) || !__has_feature(nullability)
+#error "This file requires nullability support."
+#endif
+
+// The following nonnull macros were introduced in OSX SDK 10.10.3. However,
+// the bots appear to be running something older. We define them here if they
+// aren't already defined in NSObjCRuntime.h
+#ifdef __OBJC__
+
+#include <Foundation/NSObjCRuntime.h>
+
+#if !defined(NS_ASSUME_NONNULL_BEGIN)
+#define NS_ASSUME_NONNULL_BEGIN
+#endif
+
+#if !defined(NS_ASSUME_NONNULL_END)
+#define NS_ASSUME_NONNULL_END
+#endif
+
+#endif
diff --git a/webrtc/build/objc_common.gypi b/webrtc/build/objc_common.gypi
new file mode 100644
index 0000000000..086210ee75
--- /dev/null
+++ b/webrtc/build/objc_common.gypi
@@ -0,0 +1,21 @@
+# Copyright 2016 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+# ObjC target common prefix header.
+
+{
+  'variables': {
+    'objc_prefix_file': './WebRTC-Prefix.pch',
+  },
+  'xcode_settings': {
+    'CLANG_ENABLE_OBJC_ARC': 'YES',
+    'CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS': 'YES',
+    'GCC_PREFIX_HEADER': '<(objc_prefix_file)',
+    'GCC_PRECOMPILE_PREFIX_HEADER': 'YES'
+  },
+}