diff --git a/src/execution/execute.d.ts b/src/execution/execute.d.ts
index f927d9082d..4b16654cbd 100644
--- a/src/execution/execute.d.ts
+++ b/src/execution/execute.d.ts
@@ -43,11 +43,16 @@ export interface ExecutionContext {
  *
  *   - `errors` is included when any errors occurred as a non-empty array.
  *   - `data` is the result of a successful execution of the query.
+ *   - `extensions` is reserved for adding non-standard properties.
  */
-export interface ExecutionResult<TData = { [key: string]: any }> {
+export interface ExecutionResult<
+  TData = { [key: string]: any },
+  TExtensions = { [key: string]: any }
+> {
   errors?: ReadonlyArray<GraphQLError>;
   // TS_SPECIFIC: TData. Motivation: https://github.com/graphql/graphql-js/pull/2490#issuecomment-639154229
   data?: TData | null;
+  extensions?: TExtensions;
 }
 
 export interface ExecutionArgs {
diff --git a/src/execution/execute.js b/src/execution/execute.js
index 821b6e403f..7cd8a6aeee 100644
--- a/src/execution/execute.js
+++ b/src/execution/execute.js
@@ -109,10 +109,12 @@ export type ExecutionContext = {|
  *
  *   - `errors` is included when any errors occurred as a non-empty array.
  *   - `data` is the result of a successful execution of the query.
+ *   - `extensions` is reserved for adding non-standard properties.
  */
 export type ExecutionResult = {|
   errors?: $ReadOnlyArray<GraphQLError>,
   data?: ObjMap<mixed> | null,
+  extensions?: ObjMap<mixed>,
 |};
 
 export type ExecutionArgs = {|