Warning: unnecessary check for minimum deployment target

I have a Swift class which is linked against several targets with different deployment targets, the main project has iOS 7 minimum requirement and there is an extension with iOS 8 target.

Now when I compile project, the compiler throws warning on this line of code:

    if #available(iOS 8.0, *) { ... }

"Unnecessary check for 'iOSApplicationExtension'; minimum deployment target ensures guard will always be true"

I have checked build settings options and found no switch to kill swift warnings.

I tried to define iOSApplicationExtension version target separately by this line but without success:

    if #available(iOS 8.0, iOSApplicationExtension 8.0, *) { ... }

Is there any way to suppress this annoying message?