g++ 4.8.5 compiles c++14 code silently in c++11 mode

To my surprise, the following program compiles just fine:

int main()
{ 
    int i = 4;
    [j = i]{}();
}

> g++ --std=c++11 ext.cpp
> 

The problem is that I want this to fail: Generalized Lambda Capture is a C++14 feature, and my current project has a requirement for C++11.

Now, Clang compiles this too with a warning, which I can promote to an error using -Werror=c++14-extensions. However, I can find no similar flag for g++. I can use -pedantic-errors or -Werror=pedantic, but those come with way, way more baggage.

Have I overlooked some compiler option for this compiler?