diff --git a/src/gl/scene/gl_walls.cpp b/src/gl/scene/gl_walls.cpp
index e337f1873..ae7cb70c8 100644
--- a/src/gl/scene/gl_walls.cpp
+++ b/src/gl/scene/gl_walls.cpp
@@ -217,7 +217,7 @@ void GLWall::PutPortal(int ptype)
 		if (!portal)
 		{
 			line_t *otherside = lineportal->lines[0]->mDestination;
-			if (otherside != NULL)
+			if (otherside != NULL && otherside->portalindex < linePortals.Size())
 			{
 				gl_RenderActorsInPortal(linePortalToGL[otherside->portalindex]);
 			}