Menu briefly appears when using alt+shift+ shortcut

[roblourens]

• Windows
• Set this keybinding:

{
        "key": "alt+shift+f",
        "command": "filesExplorer.findInFolder",
        "when": "explorerViewletVisible"
},

• Focus the explorer, press alt+shift+f
• The command executes correctly, but the File menu also flashes, as if alt+f is being invoked at the same time

If I use a different "when" context, this doesn't happen. Shouldn't the menu not be opened at all for alt+shift+something, only alt+something?