Android CMake toolchain bug?

I am trying to compile the native part of my Android application using CMake.

In my CMakeLists.txt file I have this declaration:

append(CMAKE_CXX_FLAGS "-std=c++11")

Which works fine when I compile the app for other platforms, but when I add the android.toolchain.cmake into the mix, this line produces:

... -fno-exceptions -fno-rtti ;-std=c++11 ...

That is a ; is for some reason added before the flag. This brakes the bash command (a call to the compiler) into two, where the first part is incomplete and the second part doesn't make sense.

How do I tell Android to use the c++11 standard?