diff --git a/tests/baselines/reference/mappedTypesAndObjects.js b/tests/baselines/reference/mappedTypesAndObjects.js
index 53b39209693..f320cc9624e 100644
--- a/tests/baselines/reference/mappedTypesAndObjects.js
+++ b/tests/baselines/reference/mappedTypesAndObjects.js
@@ -12,26 +12,37 @@ function f2<T>(x: Partial<T>, y: Readonly<T>) {
     obj = y;
 }
 
+function f3<T>(x: Partial<T>) {
+    x = {};
+}
+
 // Repro from #12900
 
 interface Base {
-   foo: { [key: string]: any };
-   bar: any;
-   baz: any;
+    foo: { [key: string]: any };
+    bar: any;
+    baz: any;
 }
 
 interface E1<T> extends Base {
-  foo: T;
+    foo: T;
 }
 
 interface Something { name: string, value: string };
 interface E2 extends Base {
-  foo: Partial<Something>;  // or other mapped type
+    foo: Partial<Something>;  // or other mapped type
 }
 
 interface E3<T> extends Base {
-  foo: Partial<T>; // or other mapped type
-}
+    foo: Partial<T>; // or other mapped type
+}
+
+// Repro from #13747
+
+class Form<T> {
+    private values: {[P in keyof T]?: T[P]} = {}
+}
+
 
 //// [mappedTypesAndObjects.js]
 function f1(x, y) {
@@ -44,12 +55,23 @@ function f2(x, y) {
     obj = x;
     obj = y;
 }
+function f3(x) {
+    x = {};
+}
 ;
+// Repro from #13747
+var Form = (function () {
+    function Form() {
+        this.values = {};
+    }
+    return Form;
+}());
 
 
 //// [mappedTypesAndObjects.d.ts]
 declare function f1<T>(x: Partial<T>, y: Readonly<T>): void;
 declare function f2<T>(x: Partial<T>, y: Readonly<T>): void;
+declare function f3<T>(x: Partial<T>): void;
 interface Base {
     foo: {
         [key: string]: any;
@@ -70,3 +92,6 @@ interface E2 extends Base {
 interface E3<T> extends Base {
     foo: Partial<T>;
 }
+declare class Form<T> {
+    private values;
+}
diff --git a/tests/baselines/reference/mappedTypesAndObjects.symbols b/tests/baselines/reference/mappedTypesAndObjects.symbols
index 1690f1b6b04..6fb5d720fb3 100644
--- a/tests/baselines/reference/mappedTypesAndObjects.symbols
+++ b/tests/baselines/reference/mappedTypesAndObjects.symbols
@@ -45,54 +45,80 @@ function f2<T>(x: Partial<T>, y: Readonly<T>) {
 >y : Symbol(y, Decl(mappedTypesAndObjects.ts, 7, 29))
 }
 
+function f3<T>(x: Partial<T>) {
+>f3 : Symbol(f3, Decl(mappedTypesAndObjects.ts, 11, 1))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 13, 12))
+>x : Symbol(x, Decl(mappedTypesAndObjects.ts, 13, 15))
+>Partial : Symbol(Partial, Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 13, 12))
+
+    x = {};
+>x : Symbol(x, Decl(mappedTypesAndObjects.ts, 13, 15))
+}
+
 // Repro from #12900
 
 interface Base {
->Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 11, 1))
+>Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 15, 1))
 
-   foo: { [key: string]: any };
->foo : Symbol(Base.foo, Decl(mappedTypesAndObjects.ts, 15, 16))
->key : Symbol(key, Decl(mappedTypesAndObjects.ts, 16, 11))
+    foo: { [key: string]: any };
+>foo : Symbol(Base.foo, Decl(mappedTypesAndObjects.ts, 19, 16))
+>key : Symbol(key, Decl(mappedTypesAndObjects.ts, 20, 12))
 
-   bar: any;
->bar : Symbol(Base.bar, Decl(mappedTypesAndObjects.ts, 16, 31))
+    bar: any;
+>bar : Symbol(Base.bar, Decl(mappedTypesAndObjects.ts, 20, 32))
 
-   baz: any;
->baz : Symbol(Base.baz, Decl(mappedTypesAndObjects.ts, 17, 12))
+    baz: any;
+>baz : Symbol(Base.baz, Decl(mappedTypesAndObjects.ts, 21, 13))
 }
 
 interface E1<T> extends Base {
->E1 : Symbol(E1, Decl(mappedTypesAndObjects.ts, 19, 1))
->T : Symbol(T, Decl(mappedTypesAndObjects.ts, 21, 13))
->Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 11, 1))
+>E1 : Symbol(E1, Decl(mappedTypesAndObjects.ts, 23, 1))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 25, 13))
+>Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 15, 1))
 
-  foo: T;
->foo : Symbol(E1.foo, Decl(mappedTypesAndObjects.ts, 21, 30))
->T : Symbol(T, Decl(mappedTypesAndObjects.ts, 21, 13))
+    foo: T;
+>foo : Symbol(E1.foo, Decl(mappedTypesAndObjects.ts, 25, 30))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 25, 13))
 }
 
 interface Something { name: string, value: string };
->Something : Symbol(Something, Decl(mappedTypesAndObjects.ts, 23, 1))
->name : Symbol(Something.name, Decl(mappedTypesAndObjects.ts, 25, 21))
->value : Symbol(Something.value, Decl(mappedTypesAndObjects.ts, 25, 35))
+>Something : Symbol(Something, Decl(mappedTypesAndObjects.ts, 27, 1))
+>name : Symbol(Something.name, Decl(mappedTypesAndObjects.ts, 29, 21))
+>value : Symbol(Something.value, Decl(mappedTypesAndObjects.ts, 29, 35))
 
 interface E2 extends Base {
->E2 : Symbol(E2, Decl(mappedTypesAndObjects.ts, 25, 52))
->Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 11, 1))
+>E2 : Symbol(E2, Decl(mappedTypesAndObjects.ts, 29, 52))
+>Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 15, 1))
 
-  foo: Partial<Something>;  // or other mapped type
->foo : Symbol(E2.foo, Decl(mappedTypesAndObjects.ts, 26, 27))
+    foo: Partial<Something>;  // or other mapped type
+>foo : Symbol(E2.foo, Decl(mappedTypesAndObjects.ts, 30, 27))
 >Partial : Symbol(Partial, Decl(lib.d.ts, --, --))
->Something : Symbol(Something, Decl(mappedTypesAndObjects.ts, 23, 1))
+>Something : Symbol(Something, Decl(mappedTypesAndObjects.ts, 27, 1))
 }
 
 interface E3<T> extends Base {
->E3 : Symbol(E3, Decl(mappedTypesAndObjects.ts, 28, 1))
->T : Symbol(T, Decl(mappedTypesAndObjects.ts, 30, 13))
->Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 11, 1))
+>E3 : Symbol(E3, Decl(mappedTypesAndObjects.ts, 32, 1))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 34, 13))
+>Base : Symbol(Base, Decl(mappedTypesAndObjects.ts, 15, 1))
 
-  foo: Partial<T>; // or other mapped type
->foo : Symbol(E3.foo, Decl(mappedTypesAndObjects.ts, 30, 30))
+    foo: Partial<T>; // or other mapped type
+>foo : Symbol(E3.foo, Decl(mappedTypesAndObjects.ts, 34, 30))
 >Partial : Symbol(Partial, Decl(lib.d.ts, --, --))
->T : Symbol(T, Decl(mappedTypesAndObjects.ts, 30, 13))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 34, 13))
 }
+
+// Repro from #13747
+
+class Form<T> {
+>Form : Symbol(Form, Decl(mappedTypesAndObjects.ts, 36, 1))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 40, 11))
+
+    private values: {[P in keyof T]?: T[P]} = {}
+>values : Symbol(Form.values, Decl(mappedTypesAndObjects.ts, 40, 15))
+>P : Symbol(P, Decl(mappedTypesAndObjects.ts, 41, 22))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 40, 11))
+>T : Symbol(T, Decl(mappedTypesAndObjects.ts, 40, 11))
+>P : Symbol(P, Decl(mappedTypesAndObjects.ts, 41, 22))
+}
+
diff --git a/tests/baselines/reference/mappedTypesAndObjects.types b/tests/baselines/reference/mappedTypesAndObjects.types
index e6f8e53f558..75f71082f31 100644
--- a/tests/baselines/reference/mappedTypesAndObjects.types
+++ b/tests/baselines/reference/mappedTypesAndObjects.types
@@ -49,19 +49,32 @@ function f2<T>(x: Partial<T>, y: Readonly<T>) {
 >y : Readonly<T>
 }
 
+function f3<T>(x: Partial<T>) {
+>f3 : <T>(x: Partial<T>) => void
+>T : T
+>x : Partial<T>
+>Partial : Partial<T>
+>T : T
+
+    x = {};
+>x = {} : {}
+>x : Partial<T>
+>{} : {}
+}
+
 // Repro from #12900
 
 interface Base {
 >Base : Base
 
-   foo: { [key: string]: any };
+    foo: { [key: string]: any };
 >foo : { [key: string]: any; }
 >key : string
 
-   bar: any;
+    bar: any;
 >bar : any
 
-   baz: any;
+    baz: any;
 >baz : any
 }
 
@@ -70,7 +83,7 @@ interface E1<T> extends Base {
 >T : T
 >Base : Base
 
-  foo: T;
+    foo: T;
 >foo : T
 >T : T
 }
@@ -84,7 +97,7 @@ interface E2 extends Base {
 >E2 : E2
 >Base : Base
 
-  foo: Partial<Something>;  // or other mapped type
+    foo: Partial<Something>;  // or other mapped type
 >foo : Partial<Something>
 >Partial : Partial<T>
 >Something : Something
@@ -95,8 +108,24 @@ interface E3<T> extends Base {
 >T : T
 >Base : Base
 
-  foo: Partial<T>; // or other mapped type
+    foo: Partial<T>; // or other mapped type
 >foo : Partial<T>
 >Partial : Partial<T>
 >T : T
 }
+
+// Repro from #13747
+
+class Form<T> {
+>Form : Form<T>
+>T : T
+
+    private values: {[P in keyof T]?: T[P]} = {}
+>values : { [P in keyof T]?: T[P] | undefined; }
+>P : P
+>T : T
+>T : T
+>P : P
+>{} : {}
+}
+