diff --git a/bitelab/__init__.py b/bitelab/__init__.py
index a85e48a..4ebd1d1 100644
--- a/bitelab/__init__.py
+++ b/bitelab/__init__.py
@@ -388,7 +388,8 @@ async def release_board(board_id, user: str = Depends(lookup_user),
 			)
 
 		env = os.environ.copy()
-		env.update({ k: v for k, v in brd.attrs.items() if k in { 'iface', 'ip', 'devfsrule' } })
+		addkeys = { 'iface', 'ip', 'devfsrule' }
+		env.update((k, brd.attrs[k]) for k in addkeys if k in brd.attrs)
 
 		sub = await asyncio.create_subprocess_exec(
 		    settings.setup_script, 'release', brd.name, user, env=env,