diff --git a/src/SPC/builder/macos/MacOSBuilder.php b/src/SPC/builder/macos/MacOSBuilder.php
index ddcfcb64..a29e9954 100644
--- a/src/SPC/builder/macos/MacOSBuilder.php
+++ b/src/SPC/builder/macos/MacOSBuilder.php
@@ -37,7 +37,7 @@ class MacOSBuilder extends UnixBuilderBase
         $this->arch_c_flags = getenv('SPC_DEFAULT_C_FLAGS');
         $this->arch_cxx_flags = getenv('SPC_DEFAULT_CXX_FLAGS');
         // cmake toolchain
-        $this->cmake_toolchain_file = SystemUtil::makeCmakeToolchainFile('Darwin', $this->getOption('arch'), $this->arch_c_flags);
+        $this->cmake_toolchain_file = SystemUtil::makeCmakeToolchainFile('Darwin', $this->getOption('arch', php_uname('m')), $this->arch_c_flags);
 
         // create pkgconfig and include dir (some libs cannot create them automatically)
         f_mkdir(BUILD_LIB_PATH . '/pkgconfig', recursive: true);