diff --git a/packages/mobx-state-tree/src/types/utility-types/optional.ts b/packages/mobx-state-tree/src/types/utility-types/optional.ts
index 04c994c0f..f9565f553 100644
--- a/packages/mobx-state-tree/src/types/utility-types/optional.ts
+++ b/packages/mobx-state-tree/src/types/utility-types/optional.ts
@@ -13,10 +13,11 @@ import {
     BaseType,
     assertIsType,
     ExtractCSTWithSTN,
-    devMode
+    devMode,
+    IAnyStateTreeNode
 } from "../../internal"
 
-type IFunctionReturn<T> = (parent: AnyObjectNode | null) => T
+type IFunctionReturn<T> = (parent: IAnyStateTreeNode | null) => T
 
 type IOptionalValue<C, T> = C | IFunctionReturn<C | T>
 
@@ -91,7 +92,9 @@ export class OptionalValue<
     getDefaultInstanceOrSnapshot(parent: AnyObjectNode | null): this["C"] | this["T"] {
         const defaultInstanceOrSnapshot =
             typeof this._defaultValue === "function"
-                ? (this._defaultValue as IFunctionReturn<this["C"] | this["T"]>)(parent)
+                ? (this._defaultValue as IFunctionReturn<this["C"] | this["T"]>)(
+                      parent && parent.storedValue
+                  )
                 : this._defaultValue
 
         // while static values are already snapshots and checked on types.optional
diff --git a/packages/mobx-state-tree/src/types/utility-types/snapshotProcessor.ts b/packages/mobx-state-tree/src/types/utility-types/snapshotProcessor.ts
index 80f6931d9..8df29342f 100644
--- a/packages/mobx-state-tree/src/types/utility-types/snapshotProcessor.ts
+++ b/packages/mobx-state-tree/src/types/utility-types/snapshotProcessor.ts
@@ -14,7 +14,8 @@ import {
     devMode,
     ComplexType,
     typeCheckFailure,
-    isUnionType
+    isUnionType,
+    IAnyStateTreeNode
 } from "../../internal"
 
 /** @hidden */
@@ -59,9 +60,12 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
         return `snapshotProcessor(${this._subtype.describe()})`
     }
 
-    private preProcessSnapshot(sn: this["C"]): IT["CreationType"] {
+    private preProcessSnapshot(
+        sn: this["C"],
+        parent: AnyObjectNode | null = null
+    ): IT["CreationType"] {
         if (this._processors.preProcessor) {
-            return this._processors.preProcessor.call(null, sn)
+            return this._processors.preProcessor.call(null, sn, parent && parent.storedValue)
         }
         return sn as any
     }
@@ -74,9 +78,13 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
         }
     }
 
-    private postProcessSnapshot(sn: IT["SnapshotType"]): this["S"] {
+    private postProcessSnapshot(sn: IT["SnapshotType"], parent: AnyObjectNode | null): this["S"] {
         if (this._processors.postProcessor) {
-            return this._processors.postProcessor.call(null, sn) as any
+            return this._processors.postProcessor.call(
+                null,
+                sn,
+                parent && parent.storedValue
+            ) as any
         }
         return sn
     }
@@ -86,9 +94,8 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
         proxyNodeTypeMethods(node.type, this, "create")
 
         const oldGetSnapshot = node.getSnapshot
-        node.getSnapshot = () => {
-            return this.postProcessSnapshot(oldGetSnapshot.call(node)) as any
-        }
+        node.getSnapshot = () =>
+            this.postProcessSnapshot(oldGetSnapshot.call(node), node.parent) as any
 
         if (!isUnionType(this._subtype)) {
             node.getReconciliationType = () => {
@@ -105,7 +112,7 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
     ): this["N"] {
         const processedInitialValue = isStateTreeNode(initialValue)
             ? initialValue
-            : this.preProcessSnapshot(initialValue)
+            : this.preProcessSnapshot(initialValue, parent)
         const node = this._subtype.instantiate(
             parent,
             subpath,
@@ -124,7 +131,7 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
     ): this["N"] {
         const node = this._subtype.reconcile(
             current,
-            isStateTreeNode(newValue) ? newValue : this.preProcessSnapshot(newValue),
+            isStateTreeNode(newValue) ? newValue : this.preProcessSnapshot(newValue, parent),
             parent,
             subpath
         ) as any
@@ -136,7 +143,7 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
 
     getSnapshot(node: this["N"], applyPostProcess: boolean = true): this["S"] {
         const sn = this._subtype.getSnapshot(node)
-        return applyPostProcess ? this.postProcessSnapshot(sn) : sn
+        return applyPostProcess ? this.postProcessSnapshot(sn, node.parent) : sn
     }
 
     isValidSnapshot(value: this["C"], context: IValidationContext): IValidationResult {
@@ -171,7 +178,7 @@ class SnapshotProcessor<IT extends IAnyType, CustomC, CustomS> extends BaseType<
         if (!(this._subtype instanceof ComplexType)) {
             return false
         }
-        const processedSn = this.preProcessSnapshot(snapshot)
+        const processedSn = this.preProcessSnapshot(snapshot, current.parent)
         return this._subtype.isMatchingSnapshotId(current as any, processedSn)
     }
 }
@@ -205,12 +212,12 @@ export interface ISnapshotProcessors<C, CustomC, S, CustomS> {
     /**
      * Function that transforms an input snapshot.
      */
-    preProcessor?(snapshot: CustomC): C
+    preProcessor?(snapshot: CustomC, parent: IAnyStateTreeNode | null): C
     /**
      * Function that transforms an output snapshot.
      * @param snapshot
      */
-    postProcessor?(snapshot: S): CustomS
+    postProcessor?(snapshot: S, parent: IAnyStateTreeNode | null): CustomS
 }
 
 /**