diff --git a/src/rendering/BuildingPlacementPreview.ts b/src/rendering/BuildingPlacementPreview.ts
index a685b1ba..51daa336 100644
--- a/src/rendering/BuildingPlacementPreview.ts
+++ b/src/rendering/BuildingPlacementPreview.ts
@@ -524,7 +524,7 @@ export class BuildingPlacementPreview {
 
     geometry.setAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));
     geometry.setAttribute('color', new THREE.Float32BufferAttribute(colors, 3));
-    geometry.setIndex(indices);
+    geometry.setIndex(new THREE.Uint32BufferAttribute(indices, 1));
 
     const material = new THREE.MeshBasicMaterial({
       vertexColors: true,
diff --git a/src/rendering/Terrain.ts b/src/rendering/Terrain.ts
index 955b0e08..5bf91a84 100644
--- a/src/rendering/Terrain.ts
+++ b/src/rendering/Terrain.ts
@@ -597,7 +597,7 @@ export class Terrain {
     geometry.setAttribute('uv', new THREE.Float32BufferAttribute(uvs, 2));
     geometry.setAttribute('aSlope', new THREE.Float32BufferAttribute(slopes, 1));
     geometry.setAttribute('aTerrainType', new THREE.Float32BufferAttribute(terrainTypes, 1));
-    geometry.setIndex(indices);
+    geometry.setIndex(new THREE.Uint32BufferAttribute(indices, 1));
     geometry.computeVertexNormals();
 
     return geometry;
@@ -765,7 +765,7 @@ export class Terrain {
     this.guardrailGeometry = new THREE.BufferGeometry();
     this.guardrailGeometry.setAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));
     this.guardrailGeometry.setAttribute('normal', new THREE.Float32BufferAttribute(normals, 3));
-    this.guardrailGeometry.setIndex(indices);
+    this.guardrailGeometry.setIndex(new THREE.Uint32BufferAttribute(indices, 1));
 
     // RTS-style yellow/orange hazard color for guardrails
     const guardrailMaterial = new THREE.MeshStandardMaterial({
diff --git a/src/rendering/WaterMesh.ts b/src/rendering/WaterMesh.ts
index 7f504564..dd8c32fd 100644
--- a/src/rendering/WaterMesh.ts
+++ b/src/rendering/WaterMesh.ts
@@ -831,7 +831,7 @@ export class WaterMesh {
     const geometry = new THREE.BufferGeometry();
     geometry.setAttribute('position', new THREE.Float32BufferAttribute(positions, 3));
     geometry.setAttribute('color', new THREE.Float32BufferAttribute(colors, 4));
-    geometry.setIndex(indices);
+    geometry.setIndex(new THREE.Uint32BufferAttribute(indices, 1));
     geometry.computeVertexNormals();
 
     // Softer blending - normal blend with lower opacity feels more natural