diff --git a/src/overlay.js b/src/overlay.js
index 0994111..d732d88 100644
--- a/src/overlay.js
+++ b/src/overlay.js
@@ -25,11 +25,11 @@ function applyOverlayToOpenAPI (spec, overlay) {
       } else {
         try {
         // It must be an update
-          jsonpath.apply(spec, a.target, (chunk) => {
-          // Deep merge using a module (built-in spread operator is only shallow)
-            const merger = mergician({ appendArrays: true })
-            return merger(chunk, a.update)
-          })
+          if (a.target === '$') {
+            spec = merger(a.update)(spec)
+          } else {
+            jsonpath.apply(spec, a.target, merger(a.update))
+          }
         } catch (ex) {
           process.stderr.write(`Error applying overlay: ${ex.message}\n`)
         // return chunk
@@ -41,6 +41,13 @@ function applyOverlayToOpenAPI (spec, overlay) {
   return spec
 }
 
+// Deep merge using a module (built-in spread operator is only shallow)
+function merger (obj) {
+  return (chunk) => {
+    return mergician({ appendArrays: true })(chunk, obj)
+  }
+}
+
 function sortOpenAPIFields (field1, field2) {
   const orderedKeys = ['info', 'servers', 'summary', 'operationId', 'tags', 'paths', 'components', 'description', 'parameters', 'responses']
 
diff --git a/test/expected/town-root-updated.yaml b/test/expected/town-root-updated.yaml
new file mode 100644
index 0000000..22fbe70
--- /dev/null
+++ b/test/expected/town-root-updated.yaml
@@ -0,0 +1,71 @@
+openapi: 3.1.0
+info:
+  version: 1.0.0
+  title: Imaginary town
+  x-overlaid: true
+servers:
+  - url: 'https://example.com'
+    description: Example server
+paths:
+  /buildings:
+    get:
+      summary: All buildings
+      operationId: buildingsList
+      responses:
+        '200':
+          description: Return all known buildings
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/Building'
+  '/buildings/{buildingId}':
+    get:
+      summary: Specific building
+      operationId: buildingById
+      parameters:
+        - name: buildingId
+          in: path
+          required: true
+          description: Which building to return
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Return a building
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Building'
+  /locations:
+    get:
+      summary: All locations
+      operationId: locationList
+      responses:
+        '200':
+          description: Returns all locations
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  type: object
+                  properties:
+                    location_id:
+                      type: integer
+                      example: 44
+                    name:
+                      type: string
+                      example: North Village
+components:
+  schemas:
+    Building:
+      type: object
+      properties:
+        building:
+          type: string
+          example: house
+        location_id:
+          type: integer
+          example: 44
diff --git a/test/overlay.test.js b/test/overlay.test.js
index 60d921f..db7d740 100644
--- a/test/overlay.test.js
+++ b/test/overlay.test.js
@@ -23,6 +23,17 @@ test('add a description and update the summary', () => {
   expect(result).toEqual(expectedOutput)
 })
 
+test('apply an overlay to the root object', () => {
+  const openapiFile = 'test/openapi/town.yaml'
+  const overlayFile = 'test/overlays/update-root.yaml'
+  const expectedFile = 'test/expected/town-root-updated.yaml'
+  const expectedOutput = fs.readFileSync(expectedFile, 'utf8')
+
+  const result = overlayFiles(openapiFile, overlayFile)
+
+  expect(result).toEqual(expectedOutput)
+})
+
 test('remove an example', () => {
   const openapiFile = 'test/openapi/town.yaml'
   const overlayFile = 'test/overlays/remove-example.yaml'
diff --git a/test/overlays/update-root.yaml b/test/overlays/update-root.yaml
new file mode 100644
index 0000000..606ec8f
--- /dev/null
+++ b/test/overlays/update-root.yaml
@@ -0,0 +1,9 @@
+overlay: 1.0.0
+info:
+  title: Structured Overlay
+  version: 1.0.0
+actions:
+- target: "$"   # Root of document
+  update:
+    info:
+      x-overlaid: true