Currently hidden by bug 924657. Once that is addressed, this is the next error. STR: Install VS2010 Launch a VC10 mozilla build window Build the tree --> Works Install VS2013 Launch a VC10 mozilla build window Build the tree --> Fail nsDataObj.h does some interface trickery due to bug 694811: http://hg.mozilla.org/mozilla-central/file/64b497e6f593/widget/windows/nsDataObj.h#l27 When VS2013 is installed, start-msvc10.bat puts the Win8.1 SDK on the INCLUDE path (so we have __IDataObjectAsyncCapability_INTERFACE_DEFINED__) but not on the LIB path (so we don't get _IID_IDataObjectAsyncCapability) It seems that this piece of start-msvc10.bat does not handle 8.1: rem The call to VS 2010 vcvars32 adds 7.x SDK paths, so prepend the 8.0 kit to give it priority if "%SDKVER%"=="8" ( ECHO Using the Windows 8.0 Developer Kit set "PATH=%SDKDIR%bin\x86;%PATH%" set "LIB=%SDKDIR%Lib\win8\um\x86;%LIB%" set "LIBPATH=%SDKDIR%Lib\win8\um\x86;%LIBPATH%" For the 8.1 SDK, the paths are "Lib\winv6.3" and not "Lib\win8". So maybe we should also check %SDKMINORVER% and adjust the folders accordingly.