diff --git a/Assets/Tests/InputSystem.Editor/CustomProcessorEnumTest.cs b/Assets/Tests/InputSystem.Editor/CustomProcessorEnumTest.cs
index f2e9cb174a..8693c35d67 100644
--- a/Assets/Tests/InputSystem.Editor/CustomProcessorEnumTest.cs
+++ b/Assets/Tests/InputSystem.Editor/CustomProcessorEnumTest.cs
@@ -108,5 +108,58 @@ public IEnumerator ProcessorEnum_ShouldSerializeByValue_WhenSerializedToAsset()
 
         yield return null;
     }
+    
+    [Test]
+    public void Migration_ShouldProduceValidActionAsset_WithEnumProcessorConverted()
+    {
+        var legacyJson = @"
+        {
+            ""name"": ""InputSystem_Actions"",
+            ""maps"": [
+                {
+                    ""name"": ""Player"",
+                    ""id"": ""df70fa95-8a34-4494-b137-73ab6b9c7d37"",
+                    ""actions"": [
+                        {
+                            ""name"": ""Move"",
+                            ""type"": ""Value"",
+                            ""id"": ""351f2ccd-1f9f-44bf-9bec-d62ac5c5f408"",
+                            ""expectedControlType"": ""Vector2"",
+                            ""processors"": ""StickDeadzone,InvertVector2(invertX=false),Custom(SomeEnum=1)"",
+                            ""interactions"": """",
+                            ""initialStateCheck"": true
+                        }
+                    ]
+                }
+            ],
+            ""controlSchemes"": [],
+            ""version"": 0
+        }";
+
+        // Parse and migrate the legacy JSON
+        var asset = InputActionAsset.FromJson(legacyJson);
+
+        // Object is valid after migration
+        Assert.That(asset, Is.Not.Null, "Migration failed to produce a valid InputActionAsset.");
+
+        var map = asset.FindActionMap("Player");
+        Assert.That(map, Is.Not.Null, "Expected Player map to exist.");
+
+        var action = map.FindAction("Move");
+        Assert.That(action, Is.Not.Null, "Expected Move action to exist.");
+
+        var processors = action.processors;
+
+        // Verify processor order and that enum was converted properly
+        Assert.That(processors, Does.Contain("StickDeadzone"), "StickDeadzone processor missing.");
+        Assert.That(processors, Does.Contain("InvertVector2(invertX=false)"), "InvertVector2 missing.");
+        Assert.That(processors, Does.Contain("Custom(SomeEnum=20)"), "Custom(SomeEnum=1) should migrate to SomeEnum=20 (OptionB).");
+
+        // Verify To JSON
+        var toJson = asset.ToJson();
+        var reloaded = InputActionAsset.FromJson(toJson);
+        Assert.That(reloaded, Is.Not.Null, "Reloaded asset after migration is null.");
+        Assert.That(reloaded.FindAction("Player/Move"), Is.Not.Null, "Reloaded asset did not contain expected Move action.");
+    }
 }
 #endif
diff --git a/Packages/com.unity.inputsystem/InputSystem/Actions/InputActionAsset.cs b/Packages/com.unity.inputsystem/InputSystem/Actions/InputActionAsset.cs
index 3b9a70fcca..3f72cab7ec 100644
--- a/Packages/com.unity.inputsystem/InputSystem/Actions/InputActionAsset.cs
+++ b/Packages/com.unity.inputsystem/InputSystem/Actions/InputActionAsset.cs
@@ -1027,43 +1027,37 @@ internal void MigrateJson(ref ReadFileJson parsedJson)
                             continue;
 
                         var list = NameAndParameters.ParseMultiple(raw).ToList();
-                        var rebuilt = new List<string>(list.Count);
+                        var converted = new List<NameAndParameters>(list.Count);
                         foreach (var nap in list)
                         {
                             var procType = InputSystem.TryGetProcessor(nap.name);
                             if (nap.parameters.Count == 0 || procType == null)
                             {
-                                rebuilt.Add(nap.ToString());
+                                converted.Add(nap);
                                 continue;
                             }
 
-                            var dict = nap.parameters.ToDictionary(p => p.name, p => p.value.ToString());
-                            var anyChanged = false;
-                            foreach (var field in procType.GetFields(BindingFlags.Public | BindingFlags.Instance).Where(f => f.FieldType.IsEnum))
+                            var updatedParameters = new List<NamedValue>(nap.parameters.Count);
+                            foreach (var param in nap.parameters)
                             {
-                                if (dict.TryGetValue(field.Name, out var ordS) && int.TryParse(ordS, out var ord))
+                                var updatedPar = param;
+                                var fieldInfo = procType.GetField(param.name, BindingFlags.Public | BindingFlags.Instance);
+                                if(fieldInfo != null && fieldInfo.FieldType.IsEnum)
                                 {
-                                    var values = Enum.GetValues(field.FieldType).Cast<object>().ToArray();
-                                    if (ord >= 0 && ord < values.Length)
+                                    var index = param.value.ToInt32();
+                                    var values = Enum.GetValues(fieldInfo.FieldType);
+                                    if(index >= 0 && index < values.Length)
                                     {
-                                        dict[field.Name] = Convert.ToInt32(values[ord]).ToString();
-                                        anyChanged = true;
+                                        var convertedValue = Convert.ToInt32(values.GetValue(index));
+                                        updatedPar = NamedValue.From(param.name, convertedValue);
                                     }
                                 }
+                                updatedParameters.Add(updatedPar);
                             }
-
-                            if (!anyChanged)
-                            {
-                                rebuilt.Add(nap.ToString());
-                            }
-                            else
-                            {
-                                var paramText = string.Join(",", dict.Select(kv => $"{kv.Key}={kv.Value}"));
-                                rebuilt.Add($"{nap.name}({paramText})");
-                            }
+                            converted.Add(NameAndParameters.Create(nap.name,  updatedParameters));
                         }
 
-                        actionJson.processors = string.Join(";", rebuilt);
+                        actionJson.processors = NameAndParameters.SerializeMultiple(converted);
                         mapJson.actions[ai] = actionJson;
                     }
                     parsedJson.maps[mi] = mapJson;
diff --git a/Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/NameAndParametersListView.cs b/Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/NameAndParametersListView.cs
index fd51f4d26e..a08feca97c 100644
--- a/Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/NameAndParametersListView.cs
+++ b/Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/NameAndParametersListView.cs
@@ -83,11 +83,7 @@ private void OnParametersChanged(ParameterListView listView, int index)
 
         private static string ToSerializableString(IEnumerable<NameAndParameters> parametersForEachListItem)
         {
-            if (parametersForEachListItem == null)
-                return string.Empty;
-
-            return string.Join(NamedValue.Separator,
-                parametersForEachListItem.Select(x => x.ToString()).ToArray());
+            return NameAndParameters.SerializeMultiple(parametersForEachListItem);
         }
 
         public override void RedrawUI(InputActionsEditorState state)
diff --git a/Packages/com.unity.inputsystem/InputSystem/Utilities/NameAndParameters.cs b/Packages/com.unity.inputsystem/InputSystem/Utilities/NameAndParameters.cs
index 15ceed089c..239bf59932 100644
--- a/Packages/com.unity.inputsystem/InputSystem/Utilities/NameAndParameters.cs
+++ b/Packages/com.unity.inputsystem/InputSystem/Utilities/NameAndParameters.cs
@@ -27,6 +27,24 @@ public override string ToString()
             return $"{name}({parameterString})";
         }
 
+        internal static string SerializeMultiple(IEnumerable<NameAndParameters> list)
+        {
+            if(list == null)
+                return string.Empty;
+
+            return string.Join(NamedValue.Separator, list.Select(x => x.ToString()).ToArray());
+        }
+
+        internal static NameAndParameters Create(string name, IList<NamedValue> parameters)
+        {
+            var result = new NameAndParameters
+            {
+                name = name,
+                parameters = new ReadOnlyArray<NamedValue>(parameters.ToArray())
+            };
+            return result;
+        }
+
         public static IEnumerable<NameAndParameters> ParseMultiple(string text)
         {
             List<NameAndParameters> list = null;