diff --git a/src/p_map.cpp b/src/p_map.cpp
index 16a5933d5..f889069f1 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -860,6 +860,20 @@ bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::Chec
 	FLineOpening open;
 
 	P_LineOpening(open, tm.thing, ld, ref, &cres.Position, cres.portalflags);
+	if (!tm.thing->Sector->PortalBlocksMovement(sector_t::ceiling))
+	{
+		sector_t *oppsec = cres.line->frontsector == tm.thing->Sector ? cres.line->backsector : cres.line->frontsector;
+		if (oppsec->PortalBlocksMovement(sector_t::ceiling))
+		{
+			double portz = tm.thing->Sector->GetPortalPlaneZ(sector_t::ceiling);
+			if (tm.thing->Z() < portz && tm.thing->Z() + tm.thing->MaxStepHeight >= portz && tm.floorz < portz)
+			{
+				// Actor is stepping through a portal.
+				tm.portalstep = true;
+				return true;
+			}
+		}
+	}
 
 	// [RH] Steep sectors count as dropoffs, if the actor touches the boundary between a steep slope and something else
 	if (!(tm.thing->flags & MF_DROPOFF) &&
@@ -2130,7 +2144,7 @@ bool P_TryMove(AActor *thing, const DVector2 &pos,
 				goto pushline;
 			}
 			else if (BlockingMobj->Top() - thing->Z() > thing->MaxStepHeight
-				|| (BlockingMobj->Sector->ceilingplane.ZatPoint(pos) - (BlockingMobj->Top()) < thing->Height)
+				|| ((BlockingMobj->Sector->ceilingplane.ZatPoint(pos) - (BlockingMobj->Top()) < thing->Height) && BlockingMobj->Sector->PortalBlocksMovement(sector_t::ceiling))
 				|| (tm.ceilingz - (BlockingMobj->Top()) < thing->Height))
 			{
 				goto pushline;