Unity-Technologies/UnityCsReference · error · ArgumentNullException

targetPrefab

Error message

targetPrefab

What it means

Thrown by AddGameObjectsToPrefabAndConnect when `targetPrefab` is null. The target defines which Prefab Asset the scene objects will be connected into, so a null target is an ArgumentNullException caught before iterating gameObjects.

Source

Thrown at Editor/Mono/Prefabs/PrefabUtility.bindings.cs:280

        [StaticAccessor("PrefabUtilityBindings", StaticAccessorType.DoubleColon)]
        [NativeMethod(ThrowsException = true)]
        extern private static GameObject SaveAsPrefabAssetAndConnect_Internal([NotNull] GameObject root, string path, out bool success);

        [StaticAccessor("PrefabUtilityBindings", StaticAccessorType.DoubleColon)]
        [NativeMethod(ThrowsException = true)]
        extern private static GameObject SavePrefabAsset_Internal([NotNull] GameObject root, out bool success);

        internal static void AddGameObjectsToPrefabAndConnect(GameObject[] gameObjects, Object targetPrefab)
        {
            if (gameObjects == null)
                throw new ArgumentNullException("gameObjects");

            if (gameObjects.Length == 0)
                throw new ArgumentException("gameObjects array is empty");

            if (targetPrefab == null)
                throw new ArgumentNullException("targetPrefab");

            if (!PrefabUtility.IsPartOfPrefabAsset(targetPrefab))
                throw new ArgumentException("Target Prefab has to be a Prefab Asset");

            Object targetPrefabInstance = null;

            var targetPrefabObject = PrefabUtility.GetPrefabAssetHandle(targetPrefab);

            foreach (GameObject go in gameObjects)
            {
                if (go == null)
                    throw new ArgumentException("GameObject in input 'gameObjects' array is null");

                if (EditorUtility.IsPersistent(go))  // Prefab asset
                    throw new ArgumentException("Game object is part of a prefab");

                var parentPrefabInstance = GetParentPrefabInstance(go);
                if (parentPrefabInstance == null)

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Assign a valid Prefab Asset reference (GameObject loaded from Assets).
2. Validate the load result is non-null after AssetDatabase.LoadAssetAtPath.
3. Check `targetPrefab != null` before calling and report a clear error if missing.

Example fix

// before
var target = AssetDatabase.LoadAssetAtPath<GameObject>("Assets/Missing.prefab");
PrefabUtility.AddGameObjectsToPrefabAndConnect(gos, target); // target null

// after
var target = AssetDatabase.LoadAssetAtPath<GameObject>("Assets/Prefabs/Enemy.prefab");
if (target == null) throw new System.IO.FileNotFoundException("Target prefab not found.");
PrefabUtility.AddGameObjectsToPrefabAndConnect(gos, target);

if (targetPrefab == null)
    throw new System.IO.FileNotFoundException("Target prefab could not be loaded.");

When it happens

Trigger: Calling AddGameObjectsToPrefabAndConnect(gos, null), or passing a target resolved from a missing/failed AssetDatabase lookup, an unassigned serialized field, or a destroyed object.

Common situations: targetPrefab loaded via AssetDatabase.LoadAssetAtPath with a wrong path (returns null). Serialized reference to a prefab that was deleted or not yet imported. Drag-and-drop target left unassigned in an editor window.

Related errors

• gameObjects
• The path is null
• gameObjects array is empty
• Target Prefab has to be a Prefab Asset
• GameObject in input 'gameObjects' array is null

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/d823cc35e9e79544. Report an issue: GitHub.