diff --git a/source/simulation2/MessageTypes.h b/source/simulation2/MessageTypes.h
index ade0b5fc33..4a2c47ab49 100644
--- a/source/simulation2/MessageTypes.h
+++ b/source/simulation2/MessageTypes.h
@@ -361,6 +361,20 @@ public:
 	int32_t i0, j0, i1, j1; // inclusive lower bound, exclusive upper bound, in tiles
 };
 
+/**
+ * Sent when ObstructionManager's view of the shape of the world has changed
+ * (changing the TILE_OUTOFBOUNDS tiles returned by Rasterise).
+ */
+class CMessageObstructionMapShapeChanged : public CMessage
+{
+public:
+	DEFAULT_MESSAGE_IMPL(ObstructionMapShapeChanged)
+
+	CMessageObstructionMapShapeChanged()
+	{
+	}
+};
+
 /**
  * Sent when territory assignments have changed.
  */
diff --git a/source/simulation2/TypeList.h b/source/simulation2/TypeList.h
index d96a408633..0c0f38237b 100644
--- a/source/simulation2/TypeList.h
+++ b/source/simulation2/TypeList.h
@@ -49,6 +49,7 @@ MESSAGE(MotionChanged)
 MESSAGE(RangeUpdate)
 MESSAGE(TerrainChanged)
 MESSAGE(WaterChanged)
+MESSAGE(ObstructionMapShapeChanged)
 MESSAGE(TerritoriesChanged)
 MESSAGE(PathResult)
 MESSAGE(ValueModification)
diff --git a/source/simulation2/components/CCmpObstructionManager.cpp b/source/simulation2/components/CCmpObstructionManager.cpp
index fe843e89fb..6494284442 100644
--- a/source/simulation2/components/CCmpObstructionManager.cpp
+++ b/source/simulation2/components/CCmpObstructionManager.cpp
@@ -443,6 +443,9 @@ public:
 	{
 		m_PassabilityCircular = enabled;
 		MakeDirtyAll();
+
+		CMessageObstructionMapShapeChanged msg;
+		GetSimContext().GetComponentManager().BroadcastMessage(msg);
 	}
 
 	virtual void SetDebugOverlay(bool enabled)
diff --git a/source/simulation2/components/CCmpPathfinder.cpp b/source/simulation2/components/CCmpPathfinder.cpp
index 1271700958..b2a321cf88 100644
--- a/source/simulation2/components/CCmpPathfinder.cpp
+++ b/source/simulation2/components/CCmpPathfinder.cpp
@@ -219,6 +219,7 @@ void CCmpPathfinder::HandleMessage(const CMessage& msg, bool UNUSED(global))
 	}
 	case MT_TerrainChanged:
 	case MT_WaterChanged:
+	case MT_ObstructionMapShapeChanged:
 	{
 		// TODO: we ought to only bother updating the dirtied region
 		m_TerrainDirty = true;
@@ -339,11 +340,6 @@ void CCmpPathfinder::UpdateGrid()
 		// Since terrain hasn't changed we only need to update the obstruction bits
 		// and can skip the rest of the data
 
-		// TODO: if ObstructionManager::SetPassabilityCircular was called at runtime
-		// (which should probably never happen, but that's not guaranteed),
-		// then TILE_OUTOFBOUNDS will change and we can't use this fast path, but
-		// currently it'll just set obstructionsDirty and we won't notice
-
 		for (u16 j = 0; j < m_MapSize; ++j)
 		{
 			for (u16 i = 0; i < m_MapSize; ++i)
diff --git a/source/simulation2/components/CCmpPathfinder_Common.h b/source/simulation2/components/CCmpPathfinder_Common.h
index 9e38a0529b..53c9562f27 100644
--- a/source/simulation2/components/CCmpPathfinder_Common.h
+++ b/source/simulation2/components/CCmpPathfinder_Common.h
@@ -175,6 +175,7 @@ public:
 		componentManager.SubscribeToMessageType(MT_RenderSubmit); // for debug overlays
 		componentManager.SubscribeToMessageType(MT_TerrainChanged);
 		componentManager.SubscribeToMessageType(MT_WaterChanged);
+		componentManager.SubscribeToMessageType(MT_ObstructionMapShapeChanged);
 		componentManager.SubscribeToMessageType(MT_TurnStart);
 	}
 
diff --git a/source/simulation2/scripting/MessageTypeConversions.cpp b/source/simulation2/scripting/MessageTypeConversions.cpp
index 658cef82ce..0f4ad3399e 100644
--- a/source/simulation2/scripting/MessageTypeConversions.cpp
+++ b/source/simulation2/scripting/MessageTypeConversions.cpp
@@ -323,6 +323,19 @@ CMessage* CMessageWaterChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterfac
 
 ////////////////////////////////
 
+jsval CMessageObstructionMapShapeChanged::ToJSVal(ScriptInterface& scriptInterface) const
+{
+	TOJSVAL_SETUP();
+	return OBJECT_TO_JSVAL(obj);
+}
+
+CMessage* CMessageObstructionMapShapeChanged::FromJSVal(ScriptInterface& UNUSED(scriptInterface), jsval UNUSED(val))
+{
+	return new CMessageObstructionMapShapeChanged();
+}
+
+////////////////////////////////
+
 jsval CMessageTerritoriesChanged::ToJSVal(ScriptInterface& scriptInterface) const
 {
 	TOJSVAL_SETUP();