diff --git a/docs/05_content_nodes.md b/docs/05_content_nodes.md
index 132a9bf2..e24c6d04 100644
--- a/docs/05_content_nodes.md
+++ b/docs/05_content_nodes.md
@@ -64,13 +64,13 @@ The `yaml-1.1` schema includes [additional collections](https://yaml.org/type/in
 
 All of the collections provide the following accessor methods:
 
-| Method                      | Returns   | Description                                                                                                                                                                                       |
-| --------------------------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| add(value)                  | `void`    | Adds a value to the collection. For `!!map` and `!!omap` the value must be a Pair instance or a `{ key, value }` object, which may not have a key that already exists in the map.                 |
-| delete(key)                 | `boolean` | Removes a value from the collection. Returns `true` if the item was found and removed.                                                                                                            |
-| get(key, [keepScalar]) | `any`     | Returns item at `key`, or `undefined` if not found. By default unwraps scalar values from their surrounding node; to disable set `keepScalar` to `true` (collections are always returned intact). |
-| has(key)                    | `boolean` | Checks if the collection includes a value with the key `key`.                                                                                                                                     |
-| set(key, value)             | `any`     | Sets a value in this collection. For `!!set`, `value` needs to be a boolean to add/remove the item from the set. When overwriting a `Scalar` value with a scalar, the original node is retained.  |
+| Method                                          | Returns   | Description                                                                                                                                                                                      |
+| ----------------------------------------------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
+| add(value), addIn(path, value)                  | `void`    | Adds a value to the collection. For `!!map` and `!!omap` the value must be a Pair instance or a `{ key, value }` object, which may not have a key that already exists in the map.                |
+| delete(key), deleteIn(path)                     | `boolean` | Removes a value from the collection. Returns `true` if the item was found and removed.                                                                                                           |
+| get(key, [keep]), getIn(path, [keep]) | `any`     | Returns value at `key`, or `undefined` if not found. By default unwraps scalar values from their surrounding node; to disable set `keep` to `true` (collections are always returned intact).     |
+| has(key), hasIn(path)                           | `boolean` | Checks if the collection includes a value with the key `key`.                                                                                                                                    |
+| set(key, value), setIn(path, value)             | `any`     | Sets a value in this collection. For `!!set`, `value` needs to be a boolean to add/remove the item from the set. When overwriting a `Scalar` value with a scalar, the original node is retained. |
 
 <!-- prettier-ignore -->
 ```js
@@ -92,7 +92,7 @@ doc.hasIn(['b', '0']) // true
 
 For all of these methods, the keys may be nodes or their wrapped scalar values (i.e. `42` will match `Scalar { value: 42 }`) . Keys for `!!seq` should be positive integers, or their string representations. `add()` and `set()` do not automatically call `doc.createNode()` to wrap the value.
 
-Each of the methods also has a variant that requires an iterable as the first parameter, and allows fetching or modifying deeper collections: `addIn(path, value)`, `deleteIn(path)`, `getIn(path, keepScalar)`, `hasIn(path)`, `setIn(path, value)`. If any intermediate node in `path` is a scalar rather than a collection, an error will be thrown. If any of the intermediate collections is not found:
+Each of the methods also has a variant that requires an iterable as the first parameter, and allows fetching or modifying deeper collections. If any intermediate node in `path` is a scalar rather than a collection, an error will be thrown. If any of the intermediate collections is not found:
 
 - `getIn` and `hasIn` will return `undefined` or `false` (respectively)
 - `addIn` and `setIn` will create missing collections; non-negative integer keys will create sequences, all other keys create maps
diff --git a/src/ast/Collection.js b/src/ast/Collection.js
index 6965cec5..9e40973d 100644
--- a/src/ast/Collection.js
+++ b/src/ast/Collection.js
@@ -4,7 +4,7 @@ import { createNode } from '../doc/createNode.js'
 import { Node } from './Node.js'
 import { Scalar } from './Scalar.js'
 
-function collectionFromPath(schema, path, value) {
+export function collectionFromPath(schema, path, value) {
   let v = value
   for (let i = path.length - 1; i >= 0; --i) {
     const k = path[i]
diff --git a/src/ast/index.js b/src/ast/index.js
index 25886c67..fada7c24 100644
--- a/src/ast/index.js
+++ b/src/ast/index.js
@@ -1,5 +1,5 @@
 export { Alias } from './Alias.js'
-export { Collection, isEmptyPath } from './Collection.js'
+export { Collection, collectionFromPath, isEmptyPath } from './Collection.js'
 export { Merge } from './Merge.js'
 export { Node } from './Node.js'
 export { Pair } from './Pair.js'
diff --git a/src/doc/Document.js b/src/doc/Document.js
index 58815c3e..48a9a0ae 100644
--- a/src/doc/Document.js
+++ b/src/doc/Document.js
@@ -4,6 +4,7 @@ import {
   Node,
   Pair,
   Scalar,
+  collectionFromPath,
   isEmptyPath,
   toJSON
 } from '../ast/index.js'
@@ -147,13 +148,21 @@ export class Document {
   }
 
   set(key, value) {
-    assertCollection(this.contents)
-    this.contents.set(key, value)
+    if (this.contents == null) {
+      this.setSchema()
+      this.contents = collectionFromPath(this.schema, [key], value)
+    } else {
+      assertCollection(this.contents)
+      this.contents.set(key, value)
+    }
   }
 
   setIn(path, value) {
     if (isEmptyPath(path)) this.contents = value
-    else {
+    else if (this.contents == null) {
+      this.setSchema()
+      this.contents = collectionFromPath(this.schema, path, value)
+    } else {
       assertCollection(this.contents)
       this.contents.setIn(path, value)
     }
diff --git a/tests/doc/collection-access.js b/tests/doc/collection-access.js
index e910c7de..95ab06a6 100644
--- a/tests/doc/collection-access.js
+++ b/tests/doc/collection-access.js
@@ -90,7 +90,7 @@ describe('Map', () => {
   test('set scalar node with anchor', () => {
     doc = YAML.parseDocument('a: &A value\nb: *A\n')
     doc.set('a', 'foo')
-    expect(doc.get('a',true)).toMatchObject({ value: 'foo' })
+    expect(doc.get('a', true)).toMatchObject({ value: 'foo' })
     expect(String(doc)).toBe('a: &A foo\nb: *A\n')
   })
 })
@@ -464,6 +464,10 @@ describe('Document', () => {
 
     doc.contents = doc.createNode('s')
     expect(() => doc.set('a', 1)).toThrow(/document contents/)
+
+    doc.contents = null
+    doc.set('a', 1)
+    expect(doc.get('a')).toBe(1)
   })
 
   test('setIn', () => {
@@ -485,5 +489,9 @@ describe('Document', () => {
 
     doc.contents = doc.createNode('s')
     expect(() => doc.setIn(['a'], 1)).toThrow(/document contents/)
+
+    doc.contents = null
+    doc.setIn(['a', 2], 1)
+    expect(doc.get('a')).toMatchObject({ items: [null, null, 1] })
   })
 })