I have the following in my flex.proj file to compile locales: <Target Name="Resources"> <Message Text="Compiling Resource Files"/> <Exec Command="$(flexsdkdir)\bin\mxmlc.bat -locale=en_US -library-path+=libs -source-path=locale\{locale} -include-resource-bundles=$(resourcebundles) -output=bin-release\resource\en_US_ResourceModule.swf" WorkingDirectory="$(MSBuildProjectDirectory)"/> <Exec Command="$(flexsdkdir)\bin\mxmlc.bat -locale=fr_FR -library-path+=libs -source-path=locale\{locale} -include-resource-bundles=$(resourcebundles) -output=bin-release\resource\fr_FR_ResourceModule.swf" WorkingDirectory="$(MSBuildProjectDirectory)"/> <Exec Command="$(flexsdkdir)\bin\mxmlc.bat -locale=en_GB -library-path+=libs -source-path=locale\{locale} -include-resource-bundles=$(resourcebundles) -output=bin-release\resource\en_GB_ResourceModule.swf" WorkingDirectory="$(MSBuildProjectDirectory)"/> <Exec Command="$(flexsdkdir)\bin\mxmlc.bat -locale=zh_Hans -library-path+=libs -source-path=locale\{locale} -include-resource-bundles=$(resourcebundles) -output=bin-release\resource\zh_Hans_ResourceModule.swf" WorkingDirectory="$(MSBuildProjectDirectory)"/>
</Target> Everything works fine except en_GB. I have checked frameworks\locale folder and en_GB is in there. Any idea what's wrong? Thanks