diff --git a/similar/main/newdemo.cpp b/similar/main/newdemo.cpp
index c22b2456b..4e6db4c19 100644
--- a/similar/main/newdemo.cpp
+++ b/similar/main/newdemo.cpp
@@ -1937,9 +1937,29 @@ static void newdemo_pop_ctrlcen_triggers()
 	for (int i = 0; i < ControlCenterTriggers.num_links; i++) {
 		const auto &&seg = vmsegptridx(ControlCenterTriggers.seg[i]);
 		const auto side = ControlCenterTriggers.side[i];
-		const auto &&csegp = vmsegptr(seg->children[side]);
+		const auto csegi = seg->children[side];
+		if (csegi == segment_none)
+		{
+			/* Some levels specify control center triggers for
+			 * segments/sides that have no wall.  `Descent 2:
+			 * Counterstrike` level 11, control center trigger 0 would
+			 * fault without this test.
+			 */
+			continue;
+		}
+		const auto &&csegp = vmsegptr(csegi);
 		auto cside = find_connect_side(seg, csegp);
-		const auto anim_num = vcwallptr(seg->sides[side].wall_num)->clip_num;
+		const auto wall_num = seg->sides[side].wall_num;
+		if (wall_num == wall_none)
+		{
+			/* Some levels specify control center triggers for
+			 * segments/sides that have no wall.  `Descent 2:
+			 * Counterstrike` level 9, control center trigger 2 would
+			 * fault without this test.
+			 */
+			continue;
+		}
+		const auto anim_num = vcwallptr(wall_num)->clip_num;
 		const auto n = WallAnims[anim_num].num_frames;
 		const auto t = WallAnims[anim_num].flags & WCF_TMAP1
 			? &side::tmap_num
diff --git a/similar/main/wall.cpp b/similar/main/wall.cpp
index c847b7894..9d2f1d1ca 100644
--- a/similar/main/wall.cpp
+++ b/similar/main/wall.cpp
@@ -1071,8 +1071,10 @@ void wall_toggle(const vmsegptridx_t segp, unsigned side)
 #endif
 		return;
 	}
-	auto wall_num = segp->sides[side].wall_num;
-	if (wall_num == wall_none) {
+	const auto wall_num = segp->sides[side].wall_num;
+	if (wall_num == wall_none)
+	{
+		LevelError("Ignoring attempt to toggle wall in segment %hu, side %u: no wall exists there.", segp.get_unchecked_index(), side);
 		return;
 	}