diff --git a/binding/lua_c/bench_test.lua b/binding/lua_c/bench_test.lua
index 7ab41b7..af1df2c 100644
--- a/binding/lua_c/bench_test.lua
+++ b/binding/lua_c/bench_test.lua
@@ -65,11 +65,15 @@ end
 -- create the searcher based on the cache-policy
 local searcher, v_index, content
 if cachePolicy == "file" then
-    searcher = xdb.new_with_file_only(dbFile)
+    searcher, err = xdb.new_with_file_only(dbFile)
+    if err ~= nil then
+        print(string.format("failed to create searcher: %s", err))
+        return
+    end
 elseif cachePolicy == "vectorIndex" then
-    v_index = xdb.load_vector_index(dbFile)
-    if v_index == nil then
-        print(string.format("failed to load vector index from '%s'", dbFile))
+    v_index, err = xdb.load_vector_index(dbFile)
+    if err ~= nil then
+        print(string.format("failed to load vector index: %s", err))
         return
     end
 
@@ -79,8 +83,8 @@ elseif cachePolicy == "vectorIndex" then
         return
     end
 elseif cachePolicy == "content" then
-    content = xdb.load_content(dbFile)
-    if content == nil then
+    content, err = xdb.load_content(dbFile)
+    if err ~= nil then
         print(string.format("failed to load xdb content from '%s'", dbFile))
         return
     end
@@ -174,4 +178,4 @@ if count > 0 then
     avg_costs = c_time / count
 end
 print(string.format("Bench finished, {cachePolicy: %s, total: %d, took: %.3f s, cost: %.3f μs/op}",
-         cachePolicy, count, (xdb.now() - s_time)/1e6, c_time / count))
+         cachePolicy, count, (xdb.now() - s_time)/1e6, c_time / count))
\ No newline at end of file
diff --git a/binding/lua_c/search_test.lua b/binding/lua_c/search_test.lua
index 62245be..0622d59 100644
--- a/binding/lua_c/search_test.lua
+++ b/binding/lua_c/search_test.lua
@@ -68,9 +68,9 @@ if cachePolicy == "file" then
         return
     end
 elseif cachePolicy == "vectorIndex" then
-    v_index = xdb.load_vector_index(dbFile)
-    if v_index == nil then
-        print(string.format("failed to load vector index from '%s'", dbFile))
+    v_index, err = xdb.load_vector_index(dbFile)
+    if err ~= nil then
+        print(string.format("failed to load vector index: %s", err))
         return
     end
 
@@ -80,8 +80,8 @@ elseif cachePolicy == "vectorIndex" then
         return
     end
 elseif cachePolicy == "content" then
-    content = xdb.load_content(dbFile)
-    if content == nil then
+    content, err = xdb.load_content(dbFile)
+    if err ~= nil then
         print(string.format("failed to load xdb content from '%s'", dbFile))
         return
     end
diff --git a/binding/lua_c/xdb_searcher.c b/binding/lua_c/xdb_searcher.c
index 9e8f67d..59268ad 100644
--- a/binding/lua_c/xdb_searcher.c
+++ b/binding/lua_c/xdb_searcher.c
@@ -152,13 +152,16 @@ static int lua_xdb_load_header_from_file(lua_State *L) {
     header = xdb_load_header_from_file(db_path);
     if (header == NULL) {
         lua_pushnil(L);
-        return 1;
+        lua_pushfstring(L, "load header from `%s`", db_path);
+        return 2;
     }
 
     // alloc the buffer.
     buffer = (xdb_buffer_t *) lua_newuserdata(L, sizeof(xdb_buffer_t));
     if (buffer == NULL) {
-        return luaL_error(L, "failed to alloc xdb buffer entry");
+        lua_pushnil(L);
+        lua_pushfstring(L, "failed to alloc xdb buffer entry");
+        return 2;
     }
 
     // init the buffer
@@ -170,8 +173,9 @@ static int lua_xdb_load_header_from_file(lua_State *L) {
     // set the metatable of the header buffer object and push onto the stack
     luaL_getmetatable(L, XDB_BUFFER_METATABLE_NAME);
     lua_setmetatable(L, -2);
+    lua_pushnil(L);
 
-    return 1;
+    return 2;
 }
 
 static int lua_xdb_load_vector_index_from_file(lua_State *L) {
@@ -184,13 +188,16 @@ static int lua_xdb_load_vector_index_from_file(lua_State *L) {
     v_index = xdb_load_vector_index_from_file(db_path);
     if (v_index == NULL) {
         lua_pushnil(L);
-        return 1;
+        lua_pushfstring(L, "load vector index from `%s`", db_path);
+        return 2;
     }
 
     // alloc the buffer.
     buffer = (xdb_buffer_t *) lua_newuserdata(L, sizeof(xdb_buffer_t));
     if (buffer == NULL) {
-        return luaL_error(L, "failed to alloc xdb buffer entry");
+        lua_pushnil(L);
+        lua_pushstring(L, "failed to alloc xdb buffer entry");
+        return 2;
     }
 
     // init the buffer
@@ -202,8 +209,9 @@ static int lua_xdb_load_vector_index_from_file(lua_State *L) {
     // set the metatable of the header buffer object and push onto the stack
     luaL_getmetatable(L, XDB_BUFFER_METATABLE_NAME);
     lua_setmetatable(L, -2);
+    lua_pushnil(L);
 
-    return 1;
+    return 2;
 }
 
 static int lua_xdb_load_content_from_file(lua_State *L) {
@@ -216,13 +224,16 @@ static int lua_xdb_load_content_from_file(lua_State *L) {
     content = xdb_load_content_from_file(db_path);
     if (content == NULL) {
         lua_pushnil(L);
-        return 1;
+        lua_pushfstring(L, "load xdb content from `%s`", db_path);
+        return 2;
     }
 
     // alloc the buffer.
     buffer = (xdb_buffer_t *) lua_newuserdata(L, sizeof(xdb_buffer_t));
     if (buffer == NULL) {
-        return luaL_error(L, "failed to alloc xdb buffer entry");
+        lua_pushnil(L);
+        lua_pushstring(L, "failed to alloc xdb buffer entry");
+        return 2;
     }
 
     // init the buffer
@@ -234,8 +245,9 @@ static int lua_xdb_load_content_from_file(lua_State *L) {
     // set the metatable of the header buffer object and push onto the stack
     luaL_getmetatable(L, XDB_BUFFER_METATABLE_NAME);
     lua_setmetatable(L, -2);
+    lua_pushnil(L);
 
-    return 1;
+    return 2;
 }
 
 // --- End of buffer api