diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 0cd80de4a78de..929d67c0c3647 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -22627,12 +22627,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
             let i = 0;
             for (const type of target.types) {
-                const targetType = getTypeOfPropertyOfType(type, propertyName);
-                if (targetType && related(getDiscriminatingType(), targetType)) {
-                    discriminable[i] = discriminable[i] === undefined ? true : discriminable[i];
-                }
-                else {
-                    discriminable[i] = false;
+                if (discriminable[i] === undefined) {
+                    const targetType = getTypeOfPropertyOfType(type, propertyName);
+                    discriminable[i] = !!(targetType && related(getDiscriminatingType(), targetType));
                 }
                 i++;
             }
diff --git a/tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt b/tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt
index 1479d824429a1..26632957ffa2a 100644
--- a/tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt
+++ b/tests/baselines/reference/assignmentCompatWithDiscriminatedUnion.errors.txt
@@ -6,10 +6,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(58,5): error TS2322: Type 'S' is not assignable to type 'T'.
   Property 'c' is missing in type 'S' but required in type '{ a: 2; b: 4 | 3; c: string; }'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts(82,5): error TS2322: Type 'S' is not assignable to type 'T'.
-  Type 'S' is not assignable to type '{ a: N; b: N; c: 2; }'.
-    Types of property 'c' are incompatible.
-      Type 'N' is not assignable to type '2'.
-        Type '0' is not assignable to type '2'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithDiscriminatedUnion.ts (3 errors) ====
@@ -107,10 +103,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
         t = s;
         ~
 !!! error TS2322: Type 'S' is not assignable to type 'T'.
-!!! error TS2322:   Type 'S' is not assignable to type '{ a: N; b: N; c: 2; }'.
-!!! error TS2322:     Types of property 'c' are incompatible.
-!!! error TS2322:       Type 'N' is not assignable to type '2'.
-!!! error TS2322:         Type '0' is not assignable to type '2'.
     }
     
     // https://github.com/Microsoft/TypeScript/issues/14865
diff --git a/tests/baselines/reference/excessPropertyCheckWithMultipleDiscriminants.errors.txt b/tests/baselines/reference/excessPropertyCheckWithMultipleDiscriminants.errors.txt
index 62f17936146a4..38ddb54475f8a 100644
--- a/tests/baselines/reference/excessPropertyCheckWithMultipleDiscriminants.errors.txt
+++ b/tests/baselines/reference/excessPropertyCheckWithMultipleDiscriminants.errors.txt
@@ -1,7 +1,7 @@
 tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(30,5): error TS2322: Type '{ type: "number"; value: number; multipleOf: number; format: string; }' is not assignable to type 'Primitive'.
   Object literal may only specify known properties, and 'multipleOf' does not exist in type 'Float'.
-tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(41,5): error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
-  Object literal may only specify known properties, and 'p3' does not exist in type '{ p1: "left"; p2: boolean; }'.
+tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(42,5): error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
+  Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
 tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(50,5): error TS2322: Type '{ p1: "left"; p2: true; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
   Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
 tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(57,5): error TS2322: Type '{ p1: "right"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
@@ -59,10 +59,10 @@ tests/cases/compiler/excessPropertyCheckWithMultipleDiscriminants.ts(136,5): err
         p1: 'left',
         p2: false,
         p3: 42,
+        p4: "hello"
         ~~
 !!! error TS2322: Type '{ p1: "left"; p2: false; p3: number; p4: string; }' is not assignable to type 'DisjointDiscriminants'.
-!!! error TS2322:   Object literal may only specify known properties, and 'p3' does not exist in type '{ p1: "left"; p2: boolean; }'.
-        p4: "hello"
+!!! error TS2322:   Object literal may only specify known properties, and 'p4' does not exist in type '{ p1: "left"; p2: true; p3: number; } | { p1: "left"; p2: boolean; }'.
     };
     
     // This has excess error because variant two is not applicable.
diff --git a/tests/baselines/reference/objectLiteralNormalization.errors.txt b/tests/baselines/reference/objectLiteralNormalization.errors.txt
index a6ffc718f913c..25c20b5c23d31 100644
--- a/tests/baselines/reference/objectLiteralNormalization.errors.txt
+++ b/tests/baselines/reference/objectLiteralNormalization.errors.txt
@@ -5,9 +5,8 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(9,1): error TS2322: Type '{ c: true; }' is not assignable to type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'.
   Type '{ c: true; }' is missing the following properties from type '{ a: number; b: string; c: boolean; }': a, b
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(17,1): error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
-  Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
-    Types of property 'a' are incompatible.
-      Type 'string' is not assignable to type 'undefined'.
+  Types of property 'b' are incompatible.
+    Type 'number' is not assignable to type 'undefined'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(18,1): error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
   Property 'b' is missing in type '{ a: number; }' but required in type '{ a: number; b: number; }'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(48,20): error TS2322: Type '2' is not assignable to type '1'.
@@ -44,9 +43,8 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
     a2 = { a: "def", b: 20 };  // Error
     ~~
 !!! error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
-!!! error TS2322:   Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
-!!! error TS2322:     Types of property 'a' are incompatible.
-!!! error TS2322:       Type 'string' is not assignable to type 'undefined'.
+!!! error TS2322:   Types of property 'b' are incompatible.
+!!! error TS2322:     Type 'number' is not assignable to type 'undefined'.
     a2 = { a: 1 };  // Error
     ~~
 !!! error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
diff --git a/tests/cases/fourslash/completionsUnionStringLiteralProperty.ts b/tests/cases/fourslash/completionsUnionStringLiteralProperty.ts
new file mode 100644
index 0000000000000..a3439d10d7efa
--- /dev/null
+++ b/tests/cases/fourslash/completionsUnionStringLiteralProperty.ts
@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+//// type Foo = { a: 0, b: 'x' } | { a: 0, b: 'y' } | { a: 1, b: 'z' };
+//// const foo: Foo = { a: 0, b: '/*1*/' }
+////
+//// type Bar = { a: 0, b: 'fx' } | { a: 0, b: 'fy' } | { a: 1, b: 'fz' };
+//// const bar: Bar = { a: 0, b: 'f/*2*/' }
+verify.completions({ marker: "1", triggerCharacter: "'", includes: [ "x", "y" ], excludes: [ "z" ] });
+verify.completions({ marker: "2", triggerCharacter: "'", includes: [ "fx", "fy" ], excludes: [ "fz" ] });
\ No newline at end of file