TypeError on Start-up

[machineghost]

I just tried to use this plugin, but got the following error on server startup.

TypeError: Cannot read properties of undefined (reading 'endsWith')
    at /home/me/project/admin/server/node_modules/postgraphile-plugin-custom-filter/src/AddFieldsToCustomFilter.js:203:23
    at SchemaBuilder.applyHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/SchemaBuilder.js:252:20)
    at fieldWithHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/makeNewBuild.js:489:33)
    at makeField (/home/me/project/admin/server/node_modules/graphile-build-pg/node8plus/plugins/PgAllRows.js:86:27)
    at /home/me/project/admin/server/node_modules/graphile-build-pg/node8plus/plugins/PgAllRows.js:184:9
    at Array.reduce (<anonymous>)
    at /home/me/project/admin/server/node_modules/graphile-build-pg/node8plus/plugins/PgAllRows.js:46:60
    at SchemaBuilder.applyHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/SchemaBuilder.js:252:20)
    at fields (/home/me/project/admin/server/node_modules/graphile-build/node8plus/makeNewBuild.js:505:40)
    at resolveThunk (/home/me/project/admin/server/node_modules/graphql/type/definition.js:438:40)
    at defineFieldMap (/home/me/project/admin/server/node_modules/graphql/type/definition.js:625:18)
    at GraphQLObjectType.getFields (/home/me/project/admin/server/node_modules/graphql/type/definition.js:579:27)
    at Object.newWithHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/makeNewBuild.js:631:36)
    at /home/me/project/admin/server/node_modules/graphile-build/node8plus/plugins/QueryPlugin.js:23:23
    at SchemaBuilder.applyHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/SchemaBuilder.js:252:20)
    at Object.newWithHooks (/home/me/project/admin/server/node_modules/graphile-build/node8plus/makeNewBuild.js:292:27)
```;

I followed the initial steps in the Readme (though I hadn't created a custom field yet), and my versions of things are:

    "postgraphile": "^4.10.0",
    "postgraphile-plugin-custom-filter": "^1.0.1",