diff --git a/src/decorator/impl/index/util.ts b/src/decorator/impl/index/util.ts
index 6dfd12362..a1bd6fbfb 100644
--- a/src/decorator/impl/index/util.ts
+++ b/src/decorator/impl/index/util.ts
@@ -47,7 +47,10 @@ export function initOrUpdateIndex(indexType: IndexType, indexData: IndexData, ta
 /**
  * @hidden
  */
-function initOrUpdateGSI(indexes: Record<string, DynamoDB.KeyType>, indexData: IndexData): Partial<PropertyMetadata<any>> {
+function initOrUpdateGSI(
+  indexes: Record<string, DynamoDB.KeyType>,
+  indexData: IndexData,
+): Partial<PropertyMetadata<any>> {
   if (indexes[indexData.name]) {
     // TODO INVESTIGATE when we throw an error we have a problem where multiple different classes extend one base class, this will be executed multiple times
     // throw new Error(
diff --git a/src/dynamo/expression/condition-expression-builder.spec.ts b/src/dynamo/expression/condition-expression-builder.spec.ts
index ce565020d..63cdf10f0 100644
--- a/src/dynamo/expression/condition-expression-builder.spec.ts
+++ b/src/dynamo/expression/condition-expression-builder.spec.ts
@@ -41,12 +41,20 @@ describe('expressions', () => {
       [undefined, undefined, {}],
       {},
       [],
-      { blub: undefined, other: undefined },
+      { blub: undefined, other: undefined, empty_arr: [] },
       new Set(arr),
     ]
 
     const filteredObj = deepFilter(obj, (item) => item !== undefined)
-    expect(filteredObj).toEqual([{ street: 'street', zip: 1524 }, [{ age: 25 }], new Set([arr[0], arr[1]])])
+    expect(filteredObj).toEqual([
+      { street: 'street', zip: 1524 },
+      [{ age: 25 }],
+      [{}],
+      {},
+      [],
+      { empty_arr: [] },
+      new Set([arr[0], arr[1]]),
+    ])
   })
 
   it('use property metadata', () => {
diff --git a/src/dynamo/expression/condition-expression-builder.ts b/src/dynamo/expression/condition-expression-builder.ts
index 9cd186886..aac94f09b 100644
--- a/src/dynamo/expression/condition-expression-builder.ts
+++ b/src/dynamo/expression/condition-expression-builder.ts
@@ -51,22 +51,22 @@ export function deepFilter(obj: any, filterFn: (value: any) => boolean): any {
     const returnArr: any[] = []
     obj.forEach((i) => {
       const item = deepFilter(i, filterFn)
-      if (item !== null) {
+      if (item !== undefined) {
         returnArr.push(item)
       }
     })
 
-    return returnArr.length ? returnArr : null
+    return returnArr
   } else if (obj instanceof Set) {
     const returnArr: any[] = []
     Array.from(obj).forEach((i) => {
       const item = deepFilter(i, filterFn)
-      if (item !== null) {
+      if (item !== undefined) {
         returnArr.push(item)
       }
     })
 
-    return returnArr.length ? new Set(returnArr) : null
+    return new Set(returnArr)
   } else if (isPlainObject(obj)) {
     const returnObj: Record<string, any> = {}
 
@@ -74,18 +74,18 @@ export function deepFilter(obj: any, filterFn: (value: any) => boolean): any {
       if (obj.hasOwnProperty(key)) {
         const value = obj[key]
         const item = deepFilter(value, filterFn)
-        if (item !== null) {
+        if (item !== undefined) {
           returnObj[key] = item
         }
       }
     }
 
-    return Object.keys(returnObj).length ? returnObj : null
+    return returnObj
   } else {
     if (filterFn(obj)) {
       return obj
     } else {
-      return null
+      return undefined
     }
   }
 }
diff --git a/src/helper/fetch-all.function.ts b/src/helper/fetch-all.function.ts
index d952af1a0..12f95c4bd 100644
--- a/src/helper/fetch-all.function.ts
+++ b/src/helper/fetch-all.function.ts
@@ -11,7 +11,10 @@ import { ScanRequest } from '../dynamo/request/scan/scan.request'
  * available. This can be used with scan and query requests.
  */
 
-export function fetchAll<T>(request: ScanRequest<T> | QueryRequest<T>, startKey?: Record<string, DynamoDB.AttributeValue>): Promise<T[]> {
+export function fetchAll<T>(
+  request: ScanRequest<T> | QueryRequest<T>,
+  startKey?: Record<string, DynamoDB.AttributeValue>,
+): Promise<T[]> {
   request.limit(ReadManyRequest.INFINITE_LIMIT)
   if (startKey) {
     request.exclusiveStartKey(startKey)
diff --git a/src/mapper/mapper.spec.ts b/src/mapper/mapper.spec.ts
index 1dfe6ed1b..8684a593a 100644
--- a/src/mapper/mapper.spec.ts
+++ b/src/mapper/mapper.spec.ts
@@ -179,7 +179,7 @@ describe('Mapper', () => {
         const employee1 = <MapAttribute<Employee>>attrValue.L[0]
         expect(employee1).toBeDefined()
         expect(keyOf(employee1)).toBe('M')
-        expect(Object.keys(employee1.M).length).toBe(2)
+        expect(Object.keys(employee1.M).length).toBe(3)
         expect(employee1.M.name).toBeDefined()
         expect(keyOf(employee1.M.name)).toBe('S')
         expect((<StringAttribute>employee1.M.name).S).toBe('max')
@@ -187,6 +187,10 @@ describe('Mapper', () => {
         expect(employee1.M.age).toBeDefined()
         expect(keyOf(employee1.M.age)).toBe('N')
         expect((<NumberAttribute>employee1.M.age).N).toBe('25')
+
+        expect(employee1.M.age).toBeDefined()
+        expect(keyOf(employee1.M.sortedSet)).toBe('NULL')
+        expect((<NullAttribute>employee1.M.sortedSet).NULL).toBe(true)
       })
 
       it('heterogenous Set without decorator should throw', () => {
@@ -713,7 +717,10 @@ describe('Mapper', () => {
       describe('model with non string/number/binary keys', () => {
         it('should accept date as HASH or RANGE key', () => {
           const now = new Date()
-          const toDbVal: Record<string, DynamoDB.AttributeValue> = toDb(new ModelWithDateAsHashKey(now), ModelWithDateAsHashKey)
+          const toDbVal: Record<string, DynamoDB.AttributeValue> = toDb(
+            new ModelWithDateAsHashKey(now),
+            ModelWithDateAsHashKey,
+          )
           expect(toDbVal.startDate.S).toBeDefined()
           expect(toDbVal.startDate.S).toEqual(now.toISOString())
         })
diff --git a/src/mapper/mapper.ts b/src/mapper/mapper.ts
index 1c6d18698..3ca3b3e5d 100644
--- a/src/mapper/mapper.ts
+++ b/src/mapper/mapper.ts
@@ -63,7 +63,7 @@ export function toDb<T>(item: T, modelConstructor?: ModelConstructor<T>): Attrib
 
     let attributeValue: Attribute | undefined | null
 
-    if (propertyValue === undefined || propertyValue === null) {
+    if (propertyValue === undefined) {
       // noop ignore because we can't map it
     } else {
       /*
@@ -274,7 +274,7 @@ export function fromDb<T>(attributeMap: Attributes<T>, modelConstructor?: ModelC
       modelValue = fromDbOne(attributeValue)
     }
 
-    if (modelValue !== null && modelValue !== undefined) {
+    if (modelValue !== undefined) {
       Reflect.set(<any>model, propertyMetadata ? propertyMetadata.name : attributeName, modelValue)
     }
   })