HDMI adapter displays wrong Desktop

Hi,

I have a MacBook Air running Yosemite. I purchased a Moshi HDMI adapter for the system to interface with a projector system we have.

When I plug in the projector's HDMI cable into the Moshi adapter the local screen of the laptop becomes "Desktop 2" while the Dock and the "real" desktop

gets displayed onto the projection screen. this is the opposite of what happens with a MacBook Pro which has an internal HDMI port.

I can't seem to be clever enough to figure out how to tell the Mac Air that the display that should remain on the local laptop is the one with the dock.

Has anyone run into this, and is there a solution?

Thanks.