Update Xcode settings
diff --git a/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj b/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
index f4e488b..a41be9f 100644
--- a/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
+++ b/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
@@ -637,7 +637,7 @@
 			attributes = {
 				LastSwiftUpdateCheck = 0710;
 				LastTestingUpgradeCheck = 0600;
-				LastUpgradeCheck = 0900;
+				LastUpgradeCheck = 0930;
 				TargetAttributes = {
 					8BBEA4A5147C727100C4ADB7 = {
 						LastSwiftMigration = 0800;
@@ -818,6 +818,7 @@
 		7461B52F0F94FAFA00A0C422 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = "$(SRCROOT)";
 				PRODUCT_NAME = ProtocolBuffers;
@@ -827,6 +828,7 @@
 		7461B5300F94FAFA00A0C422 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = "$(SRCROOT)";
 				PRODUCT_NAME = ProtocolBuffers;
@@ -837,6 +839,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = (
 					"${PROJECT_DERIVED_FILE_DIR}/protos",
@@ -863,6 +866,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = (
 					"${PROJECT_DERIVED_FILE_DIR}/protos",
@@ -1025,6 +1029,7 @@
 		F4487C4F1A9F8E0200531423 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = "$(SRCROOT)";
 				PRODUCT_NAME = TestSingleSourceBuild;
@@ -1034,6 +1039,7 @@
 		F4487C501A9F8E0200531423 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				HEADER_SEARCH_PATHS = "$(SRCROOT)";
 				PRODUCT_NAME = TestSingleSourceBuild;
@@ -1043,12 +1049,14 @@
 		F45BBC151B0CE3C6002D064D /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 			};
 			name = Debug;
 		};
 		F45BBC161B0CE3C6002D064D /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				CLANG_ENABLE_OBJC_WEAK = YES;
 			};
 			name = Release;
 		};