diff --git a/build_config.rb b/build_config.rb
index 8293092abe..58ee38b57d 100644
--- a/build_config.rb
+++ b/build_config.rb
@@ -1,12 +1,18 @@
-MRuby::Build.new do |conf|
-  # load specific toolchain settings
-
-  # Gets set by the VS command prompts.
+def detect_toolchain
   if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
-    toolchain :visualcpp
+    :visualcpp
   else
-    toolchain :gcc
+    cc = ENV['CC'] || 'cc'
+    if `#{cc} --version 2>&1` =~ /clang/i
+      :clang
+    else
+      :gcc
+    end
   end
+end
+
+MRuby::Build.new do |conf|
+  toolchain detect_toolchain
 
   enable_debug
 
@@ -85,14 +91,7 @@
 end
 
 MRuby::Build.new('host-debug') do |conf|
-  # load specific toolchain settings
-
-  # Gets set by the VS command prompts.
-  if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
-    toolchain :visualcpp
-  else
-    toolchain :gcc
-  end
+  toolchain detect_toolchain
 
   enable_debug
 
@@ -110,12 +109,7 @@
 end
 
 MRuby::Build.new('test') do |conf|
-  # Gets set by the VS command prompts.
-  if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
-    toolchain :visualcpp
-  else
-    toolchain :gcc
-  end
+  toolchain detect_toolchain
 
   enable_debug
   conf.enable_bintest
diff --git a/tasks/toolchains/gcc.rake b/tasks/toolchains/gcc.rake
index f370c0abf3..76022740b8 100644
--- a/tasks/toolchains/gcc.rake
+++ b/tasks/toolchains/gcc.rake
@@ -24,7 +24,7 @@ MRuby::Toolchain.new(:gcc) do |conf, _params|
   conf.linker do |linker|
     linker.command = ENV['LD'] || 'gcc'
     linker.flags = [ENV['LDFLAGS'] || %w()]
-    linker.libraries = %w(m)
+    linker.libraries = RUBY_PLATFORM =~ /darwin/ ? %w() : %w(m)
     linker.library_paths = []
     linker.option_library = '-l%s'
     linker.option_library_path = '-L%s'