diff --git a/lib/core.js b/lib/core.js
index 2f2dc51b067..5d77d6c031f 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -21,7 +21,7 @@ declare function decodeURIComponent(encodedURIComponent: string): string;
 declare function encodeURI(uri: string): string;
 declare function encodeURIComponent(uriComponent: string): string;
 
-type PropertyDescriptor<T> = {
+type ContraPropertyDescriptor<T> = {
     enumerable?: boolean,
     configurable?: boolean,
     writable?: boolean,
@@ -31,7 +31,33 @@ type PropertyDescriptor<T> = {
     ...
 };
 
-type PropertyDescriptorMap = { [s: string]: PropertyDescriptor<any>, ... }
+type CoPropertyDescriptor<T> = {
+    enumerable: boolean;
+    configurable: boolean;
+    writable: boolean;
+    value: T;
+} | {
+    enumerable: boolean;
+    configurable: boolean;
+    get: () => T;
+    set: (value: T) => void;
+} | {
+    enumerable: boolean;
+    configurable: boolean;
+    get: () => T;
+} | {
+    enumerable: boolean;
+    configurable: boolean;
+    set: (value: T) => void;
+};
+
+type ContraPropertyDescriptorMap = {
+  [s: string]: ContraPropertyDescriptor<any>;
+}
+
+type CoPropertyDescriptorMap = {
+  [s: string]: CoPropertyDescriptor<any>;
+}
 
 type $NotNullOrVoid =
 | number
@@ -48,9 +74,9 @@ declare class Object {
     static (o: string): String;
     static <T>(o: T): T;
     static assign: Object$Assign;
-    static create(o: any, properties?: PropertyDescriptorMap): any; // compiler magic
-    static defineProperties(o: any, properties: PropertyDescriptorMap): any;
-    static defineProperty<T>(o: any, p: any, attributes: PropertyDescriptor<T>): any;
+    static create(o: any, properties?: ContraPropertyDescriptorMap): any; // compiler magic
+    static defineProperties(o: any, properties: ContraPropertyDescriptorMap): any;
+    static defineProperty<T>(o: any, p: any, attributes: ContraPropertyDescriptor<T>): any;
     static entries(object: $NotNullOrVoid): Array<[string, mixed]>;
     static freeze<T>(o: T): T;
     static fromEntries<K, V>(entries: Iterable<[K, V] | {
@@ -59,8 +85,8 @@ declare class Object {
         ...
     }>): { [K]: V, ... };
 
-    static getOwnPropertyDescriptor<T>(o: $NotNullOrVoid, p: any): PropertyDescriptor<T> | void;
-    static getOwnPropertyDescriptors(o: {...}): PropertyDescriptorMap;
+    static getOwnPropertyDescriptor<T>(o: $NotNullOrVoid, p: any): CoPropertyDescriptor<T> | void;
+    static getOwnPropertyDescriptors(o: {...}): CoPropertyDescriptorMap;
     // This is documentation only. Object.getOwnPropertyNames is implemented in OCaml code
     // https://github.com/facebook/flow/blob/8ac01bc604a6827e6ee9a71b197bb974f8080049/src/typing/statement.ml#L6308
     static getOwnPropertyNames(o: $NotNullOrVoid): Array<string>;
@@ -849,8 +875,8 @@ type Proxy$traps<T> = {
     setPrototypeOf?: (target: T, prototype: {[any] : any, ...} | null) => boolean,
     isExtensible?: (target: T) => boolean,
     preventExtensions?: (target: T) => boolean,
-    getOwnPropertyDescriptor?: (target: T, property: string) => void | PropertyDescriptor<T>,
-    defineProperty?: (target: T, property: string, descriptor: PropertyDescriptor<T>) => boolean,
+    getOwnPropertyDescriptor?: (target: T, property: string) => void | CoPropertyDescriptor<T>,
+    defineProperty?: (target: T, property: string, descriptor: ContraPropertyDescriptor<T>) => boolean,
     has?: (target: T, key: string) => boolean,
     get?: (target: T, property: string, receiver: Proxy<T>) => any,
     set?: (target: T, property: string, value: any, receiver: Proxy<T>) => boolean,