diff --git a/src/p_map.cpp b/src/p_map.cpp
index c5bf741da..ce3fd9af2 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -6497,7 +6497,7 @@ void AActor::UpdateRenderSectorList()
 		while (!sec->PortalBlocksMovement(sector_t::ceiling))
 		{
 			double planeh = sec->GetPortalPlaneZ(sector_t::ceiling);
-			if (planeh < lasth) break;	// broken setup.
+			if (planeh <= lasth) break;	// broken setup.
 			if (Top() + SPRITE_SPACE < planeh) break;
 			lasth = planeh;
 			DVector2 newpos = Pos() + sec->GetPortalDisplacement(sector_t::ceiling);
@@ -6508,7 +6508,7 @@ void AActor::UpdateRenderSectorList()
 		while (!sec->PortalBlocksMovement(sector_t::floor))
 		{
 			double planeh = sec->GetPortalPlaneZ(sector_t::floor);
-			if (planeh > lasth) break;	// broken setup.
+			if (planeh >= lasth) break;	// broken setup.
 			if (Z() - SPRITE_SPACE > planeh) break;
 			lasth = planeh;
 			DVector2 newpos = Pos() + sec->GetPortalDisplacement(sector_t::floor);