diff --git a/src/world/generator/WorldGenerator.cpp b/src/world/generator/WorldGenerator.cpp
index 8acc76e1..f585e71b 100644
--- a/src/world/generator/WorldGenerator.cpp
+++ b/src/world/generator/WorldGenerator.cpp
@@ -449,14 +449,17 @@ void WorldGenerator::generate(voxel* voxels, int chunkX, int chunkZ) {
     generatePlacements(prototype, voxels, chunkX, chunkZ);
     generatePlants(prototype, values, voxels, chunkX, chunkZ, biomes);
 
-#ifndef NDEBUG
     for (uint i = 0; i < CHUNK_VOL; i++) {
-        blockid_t id = voxels[i].id;
+        blockid_t& id = voxels[i].id;
+        if (id == BLOCK_STRUCT_AIR) {
+            id = BLOCK_AIR;
+        }
+#ifndef NDEBUG
         if (indices.get(id) == nullptr) {
             abort();
         }
-    }
 #endif
+    }
 }
 
 void WorldGenerator::generatePlacements(
@@ -514,11 +517,7 @@ void WorldGenerator::generateStructure(
                 const auto& structVoxel = 
                     structVoxels[vox_index(x, y, z, size.x, size.z)];
                 if (structVoxel.id) {
-                    if (structVoxel.id == BLOCK_STRUCT_AIR) {
-                        voxels[vox_index(sx, sy, sz)] = {0, {}};
-                    } else {
-                        voxels[vox_index(sx, sy, sz)] = structVoxel;
-                    }
+                    voxels[vox_index(sx, sy, sz)] = structVoxel;
                 }
             }
         }