Player spawns inside nether portal frame

1.  Create portal to nether
2.  Return to overworld
3.  Listen to sounds of you dying on the "generating world" screen
4.  Be dead looking out at the land in front of your overworld portal

This is inconsistent behavior (this is the only portal I've had it happen with) and I cleared the land around the portal (i.e., it definitely is the frame that is killing me.)