diff --git a/.eslintrc.yml b/.eslintrc.yml
index 7a591d07b1..b22d39627b 100644
--- a/.eslintrc.yml
+++ b/.eslintrc.yml
@@ -16,7 +16,7 @@ rules:
   flowtype/define-flow-type: error
   flowtype/newline-after-flow-annotation: [error, always]
   flowtype/no-dupe-keys: error
-  flowtype/no-existential-type: error
+  flowtype/no-existential-type: off # checked by Flow
   flowtype/no-flow-fix-me-comments: off # TODO
   flowtype/no-mixed: off
   flowtype/no-mutable-array: off
diff --git a/.flowconfig b/.flowconfig
index 6759df1337..8adf097ea4 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -19,7 +19,7 @@ untyped-type-import=error
 nonstrict-import=off
 untyped-import=off
 unclear-type=off
-deprecated-type=off
+deprecated-type=error
 deprecated-utility=error
 dynamic-export=off
 unsafe-getters-setters=error
diff --git a/src/type/definition.js b/src/type/definition.js
index 54063189b6..2599b4ad0f 100644
--- a/src/type/definition.js
+++ b/src/type/definition.js
@@ -1,7 +1,7 @@
 // @flow strict
 
 // FIXME
-/* eslint-disable flowtype/no-existential-type */
+// flowlint deprecated-type:off
 
 import objectEntries from '../polyfills/objectEntries';
 import defineToJSON from '../jsutils/defineToJSON';