diff --git a/lib/execjs/external_runtime.rb b/lib/execjs/external_runtime.rb
index 811dd69..8a924d6 100644
--- a/lib/execjs/external_runtime.rb
+++ b/lib/execjs/external_runtime.rb
@@ -28,8 +28,15 @@ module ExecJS
         source = @runtime.compile_source(source)
 
         tmpfile = write_to_tempfile(source)
+
+        if ExecJS.cygwin?
+          filepath = `cygpath -m #{tmpfile.path}`.rstrip
+        else
+          filepath = tmpfile.path
+        end
+
         begin
-          extract_result(@runtime.exec_runtime(tmpfile.path), tmpfile.path)
+          extract_result(@runtime.exec_runtime(filepath), filepath)
         ensure
           File.unlink(tmpfile)
         end
diff --git a/lib/execjs/module.rb b/lib/execjs/module.rb
index 6d155af..8b2566a 100644
--- a/lib/execjs/module.rb
+++ b/lib/execjs/module.rb
@@ -34,5 +34,9 @@ module ExecJS
     def windows?
       @windows ||= RbConfig::CONFIG["host_os"] =~ /mswin|mingw/
     end
+
+    def cygwin?
+      @cygwin ||= RbConfig::CONFIG["host_os"] =~ /cygwin/
+    end
   end
 end