diff --git a/res/scripts/stdlib.lua b/res/scripts/stdlib.lua
index 9d29b873..47094bc7 100644
--- a/res/scripts/stdlib.lua
+++ b/res/scripts/stdlib.lua
@@ -419,8 +419,9 @@ end
 
 function start_coroutine(chunk, name)
     local co = coroutine.create(function()
-        local status, error = xpcall(chunk, function(...)
-            gui.alert(debug.traceback(), function()
+        local status, error = xpcall(chunk, function(err)
+            local fullmsg = "error: "..string.match(err, ": (.+)").."\n"..debug.traceback()
+            gui.alert(fullmsg, function()
                 if world.is_open() then
                     __vc_app.close_world()
                 else
@@ -429,7 +430,7 @@ function start_coroutine(chunk, name)
                     menu.page = "main"
                 end
             end)
-            return ...
+            return fullmsg
         end)
         if not status then
             debug.error(error)
diff --git a/src/content/PacksManager.cpp b/src/content/PacksManager.cpp
index 49c3014c..4eeaa5eb 100644
--- a/src/content/PacksManager.cpp
+++ b/src/content/PacksManager.cpp
@@ -2,6 +2,7 @@
 
 #include <queue>
 #include <sstream>
+#include <algorithm>
 
 #include "util/listutil.hpp"
 
@@ -124,7 +125,9 @@ std::vector<std::string> PacksManager::assemble(
     std::queue<const ContentPack*> queue;
     std::queue<const ContentPack*> queue2;
 
-    for (auto& name : names) {
+    std::sort(allNames.begin(), allNames.end());
+
+    for (auto& name : allNames) {
         auto found = packs.find(name);
         if (found == packs.end()) {
             throw contentpack_error(name, io::path(), "pack not found");
diff --git a/src/logic/scripting/lua/libs/libworld.cpp b/src/logic/scripting/lua/libs/libworld.cpp
index 9f640039..d18f964a 100644
--- a/src/logic/scripting/lua/libs/libworld.cpp
+++ b/src/logic/scripting/lua/libs/libworld.cpp
@@ -5,6 +5,7 @@
 #include "api_lua.hpp"
 #include "assets/AssetsLoader.hpp"
 #include "coders/json.hpp"
+#include "content/Content.hpp"
 #include "engine/Engine.hpp"
 #include "world/files/WorldFiles.hpp"
 #include "io/engine_paths.hpp"
@@ -181,7 +182,7 @@ static int l_set_chunk_data(lua::State* L) {
         return lua::pushboolean(L, false);
     }
     compressed_chunks::decode(
-        *chunk, buffer.data(), buffer.size()
+        *chunk, buffer.data(), buffer.size(), *content->getIndices()
     );
     if (controller->getChunksController()->lighting == nullptr) {
         return lua::pushboolean(L, true);
diff --git a/src/voxels/compressed_chunks.cpp b/src/voxels/compressed_chunks.cpp
index 9bc5bf7e..46ba800d 100644
--- a/src/voxels/compressed_chunks.cpp
+++ b/src/voxels/compressed_chunks.cpp
@@ -4,6 +4,7 @@
 #include "coders/gzip.hpp"
 
 #include "world/files/WorldFiles.hpp"
+#include "content/Content.hpp"
 
 inline constexpr int HAS_VOXELS = 0x1;
 inline constexpr int HAS_METADATA = 0x2;
@@ -48,7 +49,9 @@ static void read_voxel_data(ByteReader& reader, util::Buffer<ubyte>& dst) {
     extrle::decode16(rleData.data(), rleData.size(), dst.data());
 }
 
-void compressed_chunks::decode(Chunk& chunk, const ubyte* src, size_t size) {
+void compressed_chunks::decode(
+    Chunk& chunk, const ubyte* src, size_t size, const ContentIndices& indices
+) {
     ByteReader reader(src, size);
 
     ubyte flags = reader.get();
@@ -58,6 +61,18 @@ void compressed_chunks::decode(Chunk& chunk, const ubyte* src, size_t size) {
         /// world.get_chunk_data is only available in the main Lua state
         static util::Buffer<ubyte> voxelData (CHUNK_DATA_LEN);
         read_voxel_data(reader, voxelData);
+        // TODO: move somewhere in Chunk
+        auto src = reinterpret_cast<const uint16_t*>(voxelData.data());
+        for (size_t i = 0; i < CHUNK_VOL; i++) {
+            blockid_t id = dataio::le2h(src[i]);;
+            if (indices.blocks.get(id) == nullptr) {
+                throw std::runtime_error(
+                    "block data corruption (chunk: " + std::to_string(chunk.x) +
+                    ", " + std::to_string(chunk.z) + ") at " +
+                    std::to_string(i) + " id: " + std::to_string(id)
+                );
+            }
+        }
         chunk.decode(voxelData.data());
         chunk.updateHeights();
     }
diff --git a/src/voxels/compressed_chunks.hpp b/src/voxels/compressed_chunks.hpp
index dd00bc66..203cc5ef 100644
--- a/src/voxels/compressed_chunks.hpp
+++ b/src/voxels/compressed_chunks.hpp
@@ -6,6 +6,7 @@
 
 #include <vector>
 
+class ContentIndices;
 class WorldRegions;
 
 namespace compressed_chunks {
@@ -15,6 +16,11 @@ namespace compressed_chunks {
         util::Buffer<ubyte>& rleBuffer
     );
     std::vector<ubyte> encode(const Chunk& chunk);
-    void decode(Chunk& chunk, const ubyte* src, size_t size);
+    void decode(
+        Chunk& chunk,
+        const ubyte* src,
+        size_t size,
+        const ContentIndices& indices
+    );
     void save(int x, int z, std::vector<ubyte> bytes, WorldRegions& regions);
 }