Help Simple adding a GameObject to an ObjectField()

For some reason when I try to drag and drop my prefab into the object field it doesn’t stick. I’m not sure where I’m going wrong. Maybe it’s just a simple mistake. Thanks in advance.

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[ExecuteInEditMode]
public class FracObject : MonoBehaviour {
    public GameObject go;
}

using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(FracObject))]
public class FracOjectEditor : Editor {

    SerializedProperty goprop;

    private void OnEnable()
    {
        goprop = serializedObject.FindProperty("go");
    }

    public override void OnInspectorGUI()
    {
        goprop.objectReferenceValue = EditorGUILayout.ObjectField(new GUIContent("Source", "Add object to fracture"), goprop.objectReferenceValue, typeof(GameObject), false);
    }
}

Solved this one with help from @baste :

I was missing this line after objectreferencevalue();

serializedObject.ApplyModifiedProperties();

Appears to work as it should now