diff --git a/src/dynamo/expression/update-expression-builder.spec.ts b/src/dynamo/expression/update-expression-builder.spec.ts
index f23d87a4a..3aa1a476b 100644
--- a/src/dynamo/expression/update-expression-builder.spec.ts
+++ b/src/dynamo/expression/update-expression-builder.spec.ts
@@ -26,6 +26,16 @@ describe('buildUpdateExpression', () => {
       })
     })
 
+    it('should build expression for number at document path ', () => {
+      const exp = buildUpdateExpression('numberValues[0]', op, [23], [], metaDataU)
+      expect(exp).toEqual({
+        attributeNames: { '#numberValues': 'numberValues' },
+        attributeValues: { ':numberValues_at_0': { N: '23' } },
+        statement: '#numberValues[0] = #numberValues[0] + :numberValues_at_0',
+        type: 'SET',
+      })
+    })
+
     it('should throw when not number', () => {
       expect(() => buildUpdateExpression('age', op, ['notANumber'], [], metaDataS)).toThrow()
     })
@@ -43,6 +53,16 @@ describe('buildUpdateExpression', () => {
       })
     })
 
+    it('should build expression for number at document path ', () => {
+      const exp = buildUpdateExpression('numberValues[0]', op, [23], [], metaDataU)
+      expect(exp).toEqual({
+        attributeNames: { '#numberValues': 'numberValues' },
+        attributeValues: { ':numberValues_at_0': { N: '23' } },
+        statement: '#numberValues[0] = #numberValues[0] - :numberValues_at_0',
+        type: 'SET',
+      })
+    })
+
     it('should throw when not number', () => {
       expect(() => buildUpdateExpression('age', op, ['notANumber'], [], metaDataS)).toThrow()
     })
diff --git a/src/dynamo/expression/update-expression-builder.ts b/src/dynamo/expression/update-expression-builder.ts
index bd35dab43..3cd5e92db 100644
--- a/src/dynamo/expression/update-expression-builder.ts
+++ b/src/dynamo/expression/update-expression-builder.ts
@@ -99,8 +99,10 @@ function buildDefaultExpression(
 
     // special case: [same as in buildDefaultConditionExpression]
     // we have the metadata for an Array/Set of an Object,
-    // but only get a single item when using `attribute('myCollectionProp[0]').set({})`
-    if (operator.action === 'set' && /\[\d+\]$/.test(attributePath)) {
+    // but only get a single item when using list indexes in attributePath
+    // e.g. `attribute('myCollectionProp[0]').set(...)`
+    // (not exclusive to `.set(...)` but all updateActions)
+    if (/\[\d+\]$/.test(attributePath)) {
       attribute = toDbOne(values[0], getPropertyPath(propertyMetadata, attributePath), alterCollectionPropertyMetadataForSingleItem(propertyMetadata))
     } else {
       attribute = toDbOne(values[0], propertyMetadata)
diff --git a/src/dynamo/request/update/update.request.spec.ts b/src/dynamo/request/update/update.request.spec.ts
index fa98fea2d..cb3e50baa 100644
--- a/src/dynamo/request/update/update.request.spec.ts
+++ b/src/dynamo/request/update/update.request.spec.ts
@@ -53,7 +53,7 @@ describe('update request', () => {
       expect(req.params.ReturnValues).toEqual('UPDATED_OLD')
     })
 
-    it('should add operations', () => {
+    it('should add operation 1', () => {
       const now = new Date()
       const request = new UpdateRequest(<any>null, UpdateModel, 'myId')
       request.operations(update<UpdateModel>('lastUpdated').set(now))
@@ -64,6 +64,16 @@ describe('update request', () => {
         ':lastUpdated': { S: now.toISOString() },
       })
     })
+    it('should add operation 2', () => {
+      const request = new UpdateRequest(<any>null, UpdateModel, 'myId')
+      request.operations(update('numberValues[1]').incrementBy(42))
+
+      expect(request.params.UpdateExpression).toBe('SET #numberValues[1] = #numberValues[1] + :numberValues_at_1')
+      expect(request.params.ExpressionAttributeNames).toEqual({ '#numberValues': 'numberValues' })
+      expect(request.params.ExpressionAttributeValues).toEqual({
+        ':numberValues_at_1': { N: '42' },
+      })
+    })
 
     it('should allow to add multiple operations', () => {
       const request = new UpdateRequest(<any>null, UpdateModel, 'myId').operations(