diff --git a/api.swagger.yaml b/api.swagger.yaml
index 94eab8dd..83f69d67 100644
--- a/api.swagger.yaml
+++ b/api.swagger.yaml
@@ -2962,6 +2962,29 @@ paths:
         - SessionCookieHeader: []
         - APIKeyHeader: []
         - CognitoJwt: [ invotra/group_polls:read ]
+    put:
+      tags:
+        - 'group polls'
+      description: 'Update information about the group poll.'
+      responses:
+        '200':
+          description: 'The group poll was successfully updated.'
+        '400':
+          description: 'The supplied UUID was malformed.'
+        '403':
+          description: 'User is not authorized to update this group poll.'
+        '404':
+          description: 'The UUID does not correspond to an existing group poll.'
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/group-poll-schema-update'
+        required: true
+      security:
+        - SessionCookieHeader: []
+        - APIKeyHeader: []
+        - CognitoJwt: [ invotra/group_polls:write ]
     delete:
       tags:
         - 'group polls'
@@ -11614,6 +11637,13 @@ components:
             - title
             - group
             - options
+    group-poll-schema-update:
+      type: object
+      properties:
+        closing_date_timestamp:
+          description: 'The closing date timestamp for the group poll (in seconds).'
+          type: integer
+          example: 1510941596
     group-poll-schema-common:
       type: object
       properties:
@@ -11621,6 +11651,10 @@ components:
           description: 'Title of the group poll.'
           type: string
           example: 'What is your favorite food?'
+        closing_date_timestamp:
+          description: 'The closing date timestamp for the group poll (in seconds).'
+          type: integer
+          example: 1510941596
     list-schema:
       allOf:
         - $ref: '#/components/schemas/list-schema-common'