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Prefab instance with a script that automatically sets the parent of it creates a duplicate of itself after exiting Prefab mode

Scene Management


How to reproduce:
1. Download extract and open attached project (
2. Open 'SampleScene'
3. Create an empty object and name it 'parent'
4. Create an instance of 'GameObject' Prefab (object 'parent' will automatically be the parent of it)
5. De-parent the 'GameObject' prefab instance
6. Enter and exit 'GameObject' prefab mode

Expected results: The hierarchy is unchanged or 'GameObject' is the child of object 'parent'
Actual results: 'GameObject' is left unchanged but another 'GameObject' is created as a child of 'parent' with a broken connection to the prefab

Reproducible with: 2018.3.6f1, 2019.1.0b4, 2019.2.0a6

Note: If the 5th step is missed, the Prefab instance connection to the Prefab simply breaks.

  1. Response avatar

    Resolution Note (fix version 2019.2):

    This is a script error. The root of the prefab is moved out of the Prefab Mode when Start() from SetParentInEditor.cs is called due to the script is using ExecuteInEditMode.

    To fix this make sure your script handles PrefabMode. This can be done by ensuring you do not change the parent if the gameobject is part of a PreviewScene (which is used for various tools and for Prefab Mode):

    bool isPreviewSceneObject = EditorSceneManager.IsPreviewSceneObject(gameObject);
    if (!isPreviewSceneObject && !string.IsNullOrEmpty(parentName) && UnityEditor.Selection.activeInstanceID == gameObject.GetInstanceID()) {
    if (!transform.parent) transform.SetParent(parentName.GetParentObjectByName());

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