diff --git a/tests/baselines/reference/mappedTypeErrors.errors.txt b/tests/baselines/reference/mappedTypeErrors.errors.txt
index 918c6627f6..17c77fa50a 100644
--- a/tests/baselines/reference/mappedTypeErrors.errors.txt
+++ b/tests/baselines/reference/mappedTypeErrors.errors.txt
@@ -26,9 +26,19 @@ tests/cases/conformance/types/mapped/mappedTypeErrors.ts(78,59): error TS2345: A
   Object literal may only specify known properties, and 'z' does not exist in type 'Readonly<{ x: number; y: number; }>'.
 tests/cases/conformance/types/mapped/mappedTypeErrors.ts(84,58): error TS2345: Argument of type '{ x: number; y: number; z: number; }' is not assignable to parameter of type 'Partial<{ x: number; y: number; }>'.
   Object literal may only specify known properties, and 'z' does not exist in type 'Partial<{ x: number; y: number; }>'.
+tests/cases/conformance/types/mapped/mappedTypeErrors.ts(106,15): error TS2345: Argument of type '{ a: undefined; }' is not assignable to parameter of type 'Pick<Foo, "a">'.
+  Types of property 'a' are incompatible.
+    Type 'undefined' is not assignable to type 'string'.
+tests/cases/conformance/types/mapped/mappedTypeErrors.ts(107,17): error TS2345: Argument of type '{ c: boolean; }' is not assignable to parameter of type 'Pick<Foo, "a" | "b">'.
+  Object literal may only specify known properties, and 'c' does not exist in type 'Pick<Foo, "a" | "b">'.
+tests/cases/conformance/types/mapped/mappedTypeErrors.ts(124,12): error TS2345: Argument of type '{ a: undefined; }' is not assignable to parameter of type 'Pick<Foo, "a">'.
+  Types of property 'a' are incompatible.
+    Type 'undefined' is not assignable to type 'string'.
+tests/cases/conformance/types/mapped/mappedTypeErrors.ts(125,14): error TS2345: Argument of type '{ c: boolean; }' is not assignable to parameter of type 'Pick<Foo, "a" | "b">'.
+  Object literal may only specify known properties, and 'c' does not exist in type 'Pick<Foo, "a" | "b">'.
 
 
-==== tests/cases/conformance/types/mapped/mappedTypeErrors.ts (17 errors) ====
+==== tests/cases/conformance/types/mapped/mappedTypeErrors.ts (21 errors) ====
     
     interface Shape {
         name: string;
@@ -158,4 +168,59 @@ tests/cases/conformance/types/mapped/mappedTypeErrors.ts(84,58): error TS2345: A
                                                              ~~~~
 !!! error TS2345: Argument of type '{ x: number; y: number; z: number; }' is not assignable to parameter of type 'Partial<{ x: number; y: number; }>'.
 !!! error TS2345:   Object literal may only specify known properties, and 'z' does not exist in type 'Partial<{ x: number; y: number; }>'.
-    }
\ No newline at end of file
+    }
+    
+    // Verify use of Pick<T, K> for setState functions (#12793)
+    
+    interface Foo {
+        a: string;
+        b?: number;
+    }
+    
+    function setState<T, K extends keyof T>(obj: T, props: Pick<T, K>) {
+        for (let k in props) {
+            obj[k] = props[k];
+        }
+    }
+    
+    let foo: Foo = { a: "hello", b: 42 };
+    setState(foo, { a: "test", b: 43 })
+    setState(foo, { a: "hi" });
+    setState(foo, { b: undefined });
+    setState(foo, { });
+    setState(foo, foo);
+    setState(foo, { a: undefined });  // Error
+                  ~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '{ a: undefined; }' is not assignable to parameter of type 'Pick<Foo, "a">'.
+!!! error TS2345:   Types of property 'a' are incompatible.
+!!! error TS2345:     Type 'undefined' is not assignable to type 'string'.
+    setState(foo, { c: true });  // Error
+                    ~~~~~~~
+!!! error TS2345: Argument of type '{ c: boolean; }' is not assignable to parameter of type 'Pick<Foo, "a" | "b">'.
+!!! error TS2345:   Object literal may only specify known properties, and 'c' does not exist in type 'Pick<Foo, "a" | "b">'.
+    
+    class C<T> {
+        state: T;
+        setState<K extends keyof T>(props: Pick<T, K>) {
+            for (let k in props) {
+                this.state[k] = props[k];
+            }
+        }
+    }
+    
+    let c = new C<Foo>();
+    c.setState({ a: "test", b: 43 });
+    c.setState({ a: "hi" });
+    c.setState({ b: undefined });
+    c.setState({ });
+    c.setState(foo);
+    c.setState({ a: undefined });  // Error
+               ~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '{ a: undefined; }' is not assignable to parameter of type 'Pick<Foo, "a">'.
+!!! error TS2345:   Types of property 'a' are incompatible.
+!!! error TS2345:     Type 'undefined' is not assignable to type 'string'.
+    c.setState({ c: true });  // Error
+                 ~~~~~~~
+!!! error TS2345: Argument of type '{ c: boolean; }' is not assignable to parameter of type 'Pick<Foo, "a" | "b">'.
+!!! error TS2345:   Object literal may only specify known properties, and 'c' does not exist in type 'Pick<Foo, "a" | "b">'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/mappedTypeErrors.js b/tests/baselines/reference/mappedTypeErrors.js
index 4d2eadbafe..e1b458565b 100644
--- a/tests/baselines/reference/mappedTypeErrors.js
+++ b/tests/baselines/reference/mappedTypeErrors.js
@@ -83,7 +83,48 @@ function f21() {
     let x1 = objAndPartial({ x: 0, y: 0 }, { x: 1 });
     let x2 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1 });
     let x3 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1, z: 1 });  // Error
-}
+}
+
+// Verify use of Pick<T, K> for setState functions (#12793)
+
+interface Foo {
+    a: string;
+    b?: number;
+}
+
+function setState<T, K extends keyof T>(obj: T, props: Pick<T, K>) {
+    for (let k in props) {
+        obj[k] = props[k];
+    }
+}
+
+let foo: Foo = { a: "hello", b: 42 };
+setState(foo, { a: "test", b: 43 })
+setState(foo, { a: "hi" });
+setState(foo, { b: undefined });
+setState(foo, { });
+setState(foo, foo);
+setState(foo, { a: undefined });  // Error
+setState(foo, { c: true });  // Error
+
+class C<T> {
+    state: T;
+    setState<K extends keyof T>(props: Pick<T, K>) {
+        for (let k in props) {
+            this.state[k] = props[k];
+        }
+    }
+}
+
+let c = new C<Foo>();
+c.setState({ a: "test", b: 43 });
+c.setState({ a: "hi" });
+c.setState({ b: undefined });
+c.setState({ });
+c.setState(foo);
+c.setState({ a: undefined });  // Error
+c.setState({ c: true });  // Error
+
 
 //// [mappedTypeErrors.js]
 function f1(x) {
@@ -124,6 +165,37 @@ function f21() {
     var x2 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1 });
     var x3 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1, z: 1 }); // Error
 }
+function setState(obj, props) {
+    for (var k in props) {
+        obj[k] = props[k];
+    }
+}
+var foo = { a: "hello", b: 42 };
+setState(foo, { a: "test", b: 43 });
+setState(foo, { a: "hi" });
+setState(foo, { b: undefined });
+setState(foo, {});
+setState(foo, foo);
+setState(foo, { a: undefined }); // Error
+setState(foo, { c: true }); // Error
+var C = (function () {
+    function C() {
+    }
+    C.prototype.setState = function (props) {
+        for (var k in props) {
+            this.state[k] = props[k];
+        }
+    };
+    return C;
+}());
+var c = new C();
+c.setState({ a: "test", b: 43 });
+c.setState({ a: "hi" });
+c.setState({ b: undefined });
+c.setState({});
+c.setState(foo);
+c.setState({ a: undefined }); // Error
+c.setState({ c: true }); // Error
 
 
 //// [mappedTypeErrors.d.ts]
@@ -168,3 +240,14 @@ declare function objAndReadonly<T>(primary: T, secondary: Readonly<T>): T;
 declare function objAndPartial<T>(primary: T, secondary: Partial<T>): T;
 declare function f20(): void;
 declare function f21(): void;
+interface Foo {
+    a: string;
+    b?: number;
+}
+declare function setState<T, K extends keyof T>(obj: T, props: Pick<T, K>): void;
+declare let foo: Foo;
+declare class C<T> {
+    state: T;
+    setState<K extends keyof T>(props: Pick<T, K>): void;
+}
+declare let c: C<Foo>;
diff --git a/tests/cases/conformance/types/mapped/mappedTypeErrors.ts b/tests/cases/conformance/types/mapped/mappedTypeErrors.ts
index a198d4e0dc..4be6b6b098 100644
--- a/tests/cases/conformance/types/mapped/mappedTypeErrors.ts
+++ b/tests/cases/conformance/types/mapped/mappedTypeErrors.ts
@@ -84,4 +84,44 @@ function f21() {
     let x1 = objAndPartial({ x: 0, y: 0 }, { x: 1 });
     let x2 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1 });
     let x3 = objAndPartial({ x: 0, y: 0 }, { x: 1, y: 1, z: 1 });  // Error
-}
\ No newline at end of file
+}
+
+// Verify use of Pick<T, K> for setState functions (#12793)
+
+interface Foo {
+    a: string;
+    b?: number;
+}
+
+function setState<T, K extends keyof T>(obj: T, props: Pick<T, K>) {
+    for (let k in props) {
+        obj[k] = props[k];
+    }
+}
+
+let foo: Foo = { a: "hello", b: 42 };
+setState(foo, { a: "test", b: 43 })
+setState(foo, { a: "hi" });
+setState(foo, { b: undefined });
+setState(foo, { });
+setState(foo, foo);
+setState(foo, { a: undefined });  // Error
+setState(foo, { c: true });  // Error
+
+class C<T> {
+    state: T;
+    setState<K extends keyof T>(props: Pick<T, K>) {
+        for (let k in props) {
+            this.state[k] = props[k];
+        }
+    }
+}
+
+let c = new C<Foo>();
+c.setState({ a: "test", b: 43 });
+c.setState({ a: "hi" });
+c.setState({ b: undefined });
+c.setState({ });
+c.setState(foo);
+c.setState({ a: undefined });  // Error
+c.setState({ c: true });  // Error