diff --git a/levels/avaraline-strict-mode/alf/bwadi-koth.alf b/levels/avaraline-strict-mode/alf/bwadi-koth.alf
index 00d3cf33..0b8fdff4 100644
--- a/levels/avaraline-strict-mode/alf/bwadi-koth.alf
+++ b/levels/avaraline-strict-mode/alf/bwadi-koth.alf
@@ -12,7 +12,6 @@
     pHillW="hillSize"
     pHillD="hillSize"
     pHillH="4"
-    wallYon="0.001"
   />
   <include alf="logic/koth.alf" />
 </map>
diff --git a/levels/avaraline-strict-mode/alf/stratocaster-hss-koth.alf b/levels/avaraline-strict-mode/alf/stratocaster-hss-koth.alf
index cfd01311..fa67a82b 100644
--- a/levels/avaraline-strict-mode/alf/stratocaster-hss-koth.alf
+++ b/levels/avaraline-strict-mode/alf/stratocaster-hss-koth.alf
@@ -11,7 +11,6 @@
     pHillW="hillSize"
     pHillD="hillSize"
     pHillH="4"
-    wallYon="0.001"
   />
   <include alf="logic/koth.alf" />
 </map>
diff --git a/levels/avaraline-strict-mode/alf/telecaster-captures.alf b/levels/avaraline-strict-mode/alf/telecaster-captures.alf
index 958226cb..2452a13e 100644
--- a/levels/avaraline-strict-mode/alf/telecaster-captures.alf
+++ b/levels/avaraline-strict-mode/alf/telecaster-captures.alf
@@ -12,7 +12,6 @@
     outerCaptureX="24"
     outerCaptureY="10"
     outerCaptureZ="39"
-    wallYon="0.001"
   />
 
   <set
diff --git a/src/game/CForceField.cpp b/src/game/CForceField.cpp
index 349d4b00..28d9e2bd 100644
--- a/src/game/CForceField.cpp
+++ b/src/game/CForceField.cpp
@@ -77,6 +77,11 @@ CAbstractActor *CForceField::EndScript() {
         }
 
         partList[0]->isTransparent = !ReadLongVar(iVisible);
+        if (!ReadLongVar(iVisible)) {
+            // Force yon when visible is false, to hide from level previews.
+            partList[0]->yon = FIX(0.001);
+            partList[0]->usesPrivateYon = true;
+        }
 
         exitMsg = ReadLongVar(iExit);
         enterMsg = ReadLongVar(iEnter);