diff --git a/.eslintrc.yml b/.eslintrc.yml
index 667104f..614a66c 100644
--- a/.eslintrc.yml
+++ b/.eslintrc.yml
@@ -455,7 +455,7 @@ overrides:
       flowtype/no-unused-expressions: off
       flowtype/no-weak-types: [error, { any: false }]
       flowtype/require-compound-type-alias: off
-      flowtype/require-exact-type: off
+      flowtype/require-exact-type: [error, never]
       flowtype/require-indexer-name: error
       flowtype/require-inexact-type: off # checked by Flow
       flowtype/require-parameter-type: off
diff --git a/.flowconfig b/.flowconfig
index 51947ce..0e640fb 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -9,10 +9,7 @@
 <PROJECT_ROOT>/node_modules/graphql
 
 [lints]
-sketchy-null-bool=error
-sketchy-null-string=error
-sketchy-null-number=error
-sketchy-null-mixed=error
+sketchy-null=error
 sketchy-number=error
 untyped-type-import=error
 nonstrict-import=off
@@ -25,7 +22,7 @@ unnecessary-optional-chain=error
 unnecessary-invariant=error
 signature-verification-failure=error
 implicit-inexact-object=error
-ambiguous-object-type=error
+ambiguous-object-type=off
 uninitialized-instance-property=error
 default-import-access=error
 invalid-import-star-use=error
@@ -37,6 +34,7 @@ export-renamed-default=error
 [options]
 all=true
 module.use_strict=true
+exact_by_default=true
 babel_loose_array_spread=true
 experimental.const_params=true
 include_warnings=true
diff --git a/src/__tests__/starWarsData.js b/src/__tests__/starWarsData.js
index 5873ac6..832551c 100644
--- a/src/__tests__/starWarsData.js
+++ b/src/__tests__/starWarsData.js
@@ -6,10 +6,10 @@
  * JSON objects in a more complex demo.
  */
 
-type Ship = {|
+type Ship = {
   id: string,
   name: string,
-|};
+};
 
 const allShips: Array<Ship> = [
   { id: '1', name: 'X-Wing' },
@@ -25,11 +25,11 @@ const allShips: Array<Ship> = [
   { id: '8', name: 'Executor' },
 ];
 
-type Faction = {|
+type Faction = {
   id: string,
   name: string,
   ships: Array<string>,
-|};
+};
 
 const rebels: Faction = {
   id: '1',
diff --git a/src/connection/arrayConnection.js b/src/connection/arrayConnection.js
index f4adff8..a172973 100644
--- a/src/connection/arrayConnection.js
+++ b/src/connection/arrayConnection.js
@@ -6,10 +6,10 @@ import type {
   ConnectionCursor,
 } from './connection';
 
-type ArraySliceMetaInfo = {|
+type ArraySliceMetaInfo = {
   sliceStart: number,
   arrayLength: number,
-|};
+};
 
 /**
  * A simple function that accepts an array and connection arguments, and returns
diff --git a/src/connection/connection.js b/src/connection/connection.js
index 5a854fa..0723d6b 100644
--- a/src/connection/connection.js
+++ b/src/connection/connection.js
@@ -73,19 +73,19 @@ export type ConnectionArguments = {
   ...
 };
 
-type ConnectionConfig = {|
+type ConnectionConfig = {
   name?: string,
   nodeType: GraphQLNamedType | GraphQLNonNull<GraphQLNamedType>,
   resolveNode?: GraphQLFieldResolver<any, any>,
   resolveCursor?: GraphQLFieldResolver<any, any>,
   edgeFields?: Thunk<GraphQLFieldConfigMap<any, any>>,
   connectionFields?: Thunk<GraphQLFieldConfigMap<any, any>>,
-|};
+};
 
-type GraphQLConnectionDefinitions = {|
+type GraphQLConnectionDefinitions = {
   edgeType: GraphQLObjectType,
   connectionType: GraphQLObjectType,
-|};
+};
 
 function resolveMaybeThunk<T>(thingOrThunk: Thunk<T>): T {
   return typeof thingOrThunk === 'function'
@@ -143,18 +143,18 @@ export function connectionDefinitions(
 /**
  * A type designed to be exposed as a `Connection` over GraphQL.
  */
-export type Connection<T> = {|
+export type Connection<T> = {
   edges: Array<Edge<T>>,
   pageInfo: PageInfo,
-|};
+};
 
 /**
  * A type designed to be exposed as a `Edge` over GraphQL.
  */
-export type Edge<T> = {|
+export type Edge<T> = {
   node: T,
   cursor: ConnectionCursor,
-|};
+};
 
 /**
  * The common page info type used by all connections.
@@ -185,9 +185,9 @@ const pageInfoType = new GraphQLObjectType({
 /**
  * A type designed to be exposed as `PageInfo` over GraphQL.
  */
-export type PageInfo = {|
+export type PageInfo = {
   startCursor: ConnectionCursor | null,
   endCursor: ConnectionCursor | null,
   hasPreviousPage: boolean,
   hasNextPage: boolean,
-|};
+};
diff --git a/src/mutation/mutation.js b/src/mutation/mutation.js
index 8ccef30..2a62a39 100644
--- a/src/mutation/mutation.js
+++ b/src/mutation/mutation.js
@@ -38,7 +38,7 @@ function resolveMaybeThunk<T>(thingOrThunk: Thunk<T>): T {
  * input field, and it should return an Object with a key for each
  * output field. It may return synchronously, or return a Promise.
  */
-type MutationConfig = {|
+type MutationConfig = {
   name: string,
   description?: string,
   deprecationReason?: string,
@@ -46,7 +46,7 @@ type MutationConfig = {|
   inputFields: Thunk<GraphQLInputFieldConfigMap>,
   outputFields: Thunk<GraphQLFieldConfigMap<any, any>>,
   mutateAndGetPayload: MutationFn,
-|};
+};
 
 /**
  * Returns a GraphQLFieldConfig for the mutation described by the
diff --git a/src/node/node.js b/src/node/node.js
index 0efefae..b76eddf 100644
--- a/src/node/node.js
+++ b/src/node/node.js
@@ -13,11 +13,11 @@ import type {
 
 import { base64, unbase64 } from '../utils/base64';
 
-type GraphQLNodeDefinitions<TContext> = {|
+type GraphQLNodeDefinitions<TContext> = {
   nodeInterface: GraphQLInterfaceType,
   nodeField: GraphQLFieldConfig<mixed, TContext>,
   nodesField: GraphQLFieldConfig<mixed, TContext>,
-|};
+};
 
 /**
  * Given a function to map from an ID to an underlying object, and a function
@@ -75,10 +75,10 @@ export function nodeDefinitions<TContext>(
   return { nodeInterface, nodeField, nodesField };
 }
 
-type ResolvedGlobalId = {|
+type ResolvedGlobalId = {
   type: string,
   id: string,
-|};
+};
 
 /**
  * Takes a type name and an ID specific to that type name, and returns a
diff --git a/src/node/plural.js b/src/node/plural.js
index 512d424..6d0f2f1 100644
--- a/src/node/plural.js
+++ b/src/node/plural.js
@@ -7,7 +7,7 @@ import type {
   GraphQLResolveInfo,
 } from 'graphql';
 
-type PluralIdentifyingRootFieldConfig = {|
+type PluralIdentifyingRootFieldConfig = {
   argName: string,
   inputType: GraphQLInputType,
   outputType: GraphQLOutputType,
@@ -17,7 +17,7 @@ type PluralIdentifyingRootFieldConfig = {|
     info: GraphQLResolveInfo,
   ) => mixed,
   description?: string,
-|};
+};
 
 export function pluralIdentifyingRootField(
   config: PluralIdentifyingRootFieldConfig,