diff --git a/Client/mods/deathmatch/logic/luadefs/CLuaEngineDefs.cpp b/Client/mods/deathmatch/logic/luadefs/CLuaEngineDefs.cpp
index d97e644810..61ab0e30a6 100644
--- a/Client/mods/deathmatch/logic/luadefs/CLuaEngineDefs.cpp
+++ b/Client/mods/deathmatch/logic/luadefs/CLuaEngineDefs.cpp
@@ -1959,8 +1959,8 @@ int CLuaEngineDefs::EngineGetModelPhysicalPropertiesGroup(lua_State* luaVM)
 int CLuaEngineDefs::EngineSetModelPhysicalPropertiesGroup(lua_State* luaVM)
 {
     //  bool engineSetModelPhysicalPropertiesGroup ( int modelID, int newGroup )
-    int          iModelID;
-    unsigned int iNewGroup;
+    int iModelID;
+    int iNewGroup;
 
     CScriptArgReader argStream(luaVM);
     argStream.ReadNumber(iModelID);
@@ -1974,9 +1974,9 @@ int CLuaEngineDefs::EngineSetModelPhysicalPropertiesGroup(lua_State* luaVM)
             return luaL_error(luaVM, argStream.GetFullErrorMessage());
         }
 
-        if (iNewGroup < 0 || iNewGroup > 159)
+        if (iNewGroup < -1 || iNewGroup > 159)
         {
-            argStream.SetCustomError("Expected group ID in range [0-159] at argument 1");
+            argStream.SetCustomError("Expected group ID in range [0-159] or -1 at argument 1");
             return luaL_error(luaVM, argStream.GetFullErrorMessage());
         }