build fails with aeson-2.0

[juhp]

servant-github-webhook> /tmp/stack-6e5db10e91215d62/servant-github-webhook-0.4.2.0/src/Servant/GitHub/Webhook.hs:228:52: error:
servant-github-webhook>     • Couldn't match type: Data.Aeson.KeyMap.KeyMap Value
servant-github-webhook>                      with: HashMap.HashMap k0 Value
servant-github-webhook>       Expected: HashMap.HashMap k0 Value
servant-github-webhook>         Actual: AesonType.Object
servant-github-webhook>     • In the second argument of ‘HashMap.lookup’, namely ‘o’
servant-github-webhook>       In a stmt of a 'do' block:
servant-github-webhook>         Object r <- HashMap.lookup "repository" o
servant-github-webhook>       In the expression:
servant-github-webhook>         do Object r <- HashMap.lookup "repository" o
servant-github-webhook>            String n <- HashMap.lookup "full_name" r
servant-github-webhook>            pure n
servant-github-webhook>     |
servant-github-webhook> 228 |         do Object r <- HashMap.lookup "repository" o
servant-github-webhook>     |                                                    ^
servant-github-webhook> 
servant-github-webhook> /tmp/stack-6e5db10e91215d62/servant-github-webhook-0.4.2.0/src/Servant/GitHub/Webhook.hs:229:51: error:
servant-github-webhook>     • Couldn't match type: Data.Aeson.KeyMap.KeyMap Value
servant-github-webhook>                      with: HashMap.HashMap k1 Value
servant-github-webhook>       Expected: HashMap.HashMap k1 Value
servant-github-webhook>         Actual: AesonType.Object
servant-github-webhook>     • In the second argument of ‘HashMap.lookup’, namely ‘r’
servant-github-webhook>       In a stmt of a 'do' block: String n <- HashMap.lookup "full_name" r
servant-github-webhook>       In the expression:
servant-github-webhook>         do Object r <- HashMap.lookup "repository" o
servant-github-webhook>            String n <- HashMap.lookup "full_name" r
servant-github-webhook>            pure n
servant-github-webhook>     |
servant-github-webhook> 229 |            String n <- HashMap.lookup "full_name" r
servant-github-webhook>     |                                                   ^