diff --git a/include/grpc/impl/codegen/port_platform.h b/include/grpc/impl/codegen/port_platform.h
index ef0260bd7a8..c1bada11df5 100644
--- a/include/grpc/impl/codegen/port_platform.h
+++ b/include/grpc/impl/codegen/port_platform.h
@@ -204,16 +204,22 @@
 #if TARGET_OS_IPHONE
 #define GPR_PLATFORM_STRING "ios"
 #define GPR_CPU_IPHONE 1
-#define GPR_STDCPP_TLS 1
 #define GRPC_CFSTREAM 1
 /* the c-ares resolver isn't safe to enable on iOS */
 #define GRPC_ARES 0
 #else /* TARGET_OS_IPHONE */
 #define GPR_PLATFORM_STRING "osx"
 #define GPR_CPU_POSIX 1
-#define GPR_STDCPP_TLS 1
 #define GPR_POSIX_CRASH_HANDLER 1
 #endif
+#ifdef __has_feature
+#if __has_feature(cxx_thread_local)
+#define GPR_STDCPP_TLS 1
+#endif
+#endif
+#ifndef GPR_STDCPP_TLS
+#define GPR_PTHREAD_TLS 1
+#endif
 #define GPR_APPLE 1
 #define GPR_GCC_ATOMIC 1
 #define GPR_POSIX_LOG 1
diff --git a/tools/internal_ci/helper_scripts/prepare_build_macos_rc b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
index 207a19c94e4..3599dd3e333 100644
--- a/tools/internal_ci/helper_scripts/prepare_build_macos_rc
+++ b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
@@ -62,13 +62,11 @@ if [ "${PREPARE_BUILD_INSTALL_DEPS_OBJC}" == "true" ]
 then
   # cocoapods
   export LANG=en_US.UTF-8
+  time gem install cocoapods --version 1.7.2 --no-document
   # pre-fetch cocoapods master repo's most recent commit only
   mkdir -p ~/.cocoapods/repos
   time git clone --depth 1 https://github.com/CocoaPods/Specs.git ~/.cocoapods/repos/master
 
-  # set xcode version for Obj-C tests
-  sudo xcode-select -switch /Applications/Xcode_9.2.app/Contents/Developer/
-
   # Needed for ios-binary-size
   time pip install --user pyyaml pyjwt cryptography requests
 
@@ -113,9 +111,6 @@ then
   export NUGET_XMLDOC_MODE=skip
   export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=true
   export DOTNET_CLI_TELEMETRY_OPTOUT=true
-
-  # Xcode 10+ doesn't support building for i386 architecture
-  sudo xcode-select -switch /Applications/Xcode_9.2.app/Contents/Developer/
 fi
 
 # PHP tests currently require using an older version of PHPUnit