#pragma warning is not suppressing a warning

I haven't seen this particular warning, but in Visual Studio, you can disable specific warnings via project properties (i.e., not pragma). Disabling them that way seems to be "stronger" than disabling them via a pragma. You might do that for just the one file you're using.

Of course, warnings frequently tell you something useful, so this would really be a last resort.

Generate a preprocessed file and you'll probably find that some other header file's re-enabling the warning.