1 files changed, 8 insertions, 0 deletions
diff --git a/ext/win32ole/extconf.rb b/ext/win32ole/extconf.rb
index 1a17524d0a..52c3d6bdfb 100644
--- a/ext/win32ole/extconf.rb
+++ b/ext/win32ole/extconf.rb
@@ -23,6 +23,14 @@ def create_win32ole_makefile
     unless have_type("IMultiLanguage2", "mlang.h")
       have_type("IMultiLanguage", "mlang.h")
     end
+    spec = nil
+    checking_for('thread_specific', '%s') do
+      spec = %w[__declspec(thread) __thread].find {|th|
+        try_compile("#{th} int foo;", "", :werror => true)
+      }
+      spec or 'no'
+    end
+    $defs << "-DRB_THREAD_SPECIFIC=#{spec}" if spec
     create_makefile("win32ole")
   end
 end