diff --git a/src/p_map.cpp b/src/p_map.cpp
index 7d5a79de8..16d8ac564 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -898,7 +898,9 @@ bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::Chec
 		}
 
 		// check if the actor can step through the ceiling portal. In this case one-sided lines in the current area should not block
-		if (!cres.line->frontsector->PortalBlocksMovement(sector_t::ceiling))
+		// Use the same rules for stepping through a portal as for non-portal case.
+		bool ismissile = (tm.thing->flags & MF_MISSILE) && !(tm.thing->flags6 & MF6_STEPMISSILE) && !(tm.thing->flags3 & MF3_FLOORHUGGER);
+		if (!ismissile && !cres.line->frontsector->PortalBlocksMovement(sector_t::ceiling))
 		{
 			double portz = cres.line->frontsector->GetPortalPlaneZ(sector_t::ceiling);
 			if (tm.thing->Z() < portz && tm.thing->Z() + tm.thing->MaxStepHeight >= portz && tm.floorz < portz)
@@ -1008,7 +1010,9 @@ 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))
+	// Use the same rules for stepping through a portal as for non-portal case.
+	bool ismissile = (tm.thing->flags & MF_MISSILE) && !(tm.thing->flags6 & MF6_STEPMISSILE) && !(tm.thing->flags3 & MF3_FLOORHUGGER);
+	if (!ismissile && !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))
@@ -2707,8 +2711,8 @@ bool P_TryMove(AActor *thing, const DVector2 &pos,
 		FLinkContext ctx;
 		DVector3 oldpos = thing->Pos();
 		thing->UnlinkFromWorld(&ctx);
-		thing->SetXYZ(thing->PosRelative(thing->Sector->GetOppositePortalGroup(sector_t::ceiling)));
-		thing->Prev = thing->Pos() - oldpos;
+		thing->SetXYZ(thing->PosRelative(tm.portalgroup));
+		thing->Prev += thing->Pos() - oldpos;
 		thing->Sector = P_PointInSector(thing->Pos());
 		thing->PrevPortalGroup = thing->Sector->PortalGroup;
 		thing->LinkToWorld(&ctx);