Created Unassigned: UnauthorizedAccess at CopyPixels() [21619]

Hello. I found out that calling CopyPixels() (or in fact any functions that invokes this methods internally) causes System.UnauthorizedAccessException to occur. I've managed to trace the error: it all goes wrong at line 160 in BitmapContext.cs (dstPtr[i] = (srcPtr[i * 4 + 3] << 24) etc.).
I'm using Windows Phone 8.1 Runtime SDK. This bug occurs on both emulator and an actual device.