diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 10376e268a4f0..5c53409dcaa09 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -27888,24 +27888,22 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         for (const type of types) {
             if (type.flags & (TypeFlags.Object | TypeFlags.Intersection | TypeFlags.InstantiableNonPrimitive)) {
                 const discriminant = getTypeOfPropertyOfType(type, name);
-                if (discriminant) {
-                    if (!isLiteralType(discriminant)) {
-                        return undefined;
-                    }
-                    let duplicate = false;
-                    forEachType(discriminant, t => {
-                        const id = getTypeId(getRegularTypeOfLiteralType(t));
-                        const existing = map.get(id);
-                        if (!existing) {
-                            map.set(id, type);
-                        }
-                        else if (existing !== unknownType) {
-                            map.set(id, unknownType);
-                            duplicate = true;
-                        }
-                    });
-                    if (!duplicate) count++;
+                if (!discriminant || !isLiteralType(discriminant)) {
+                    return undefined;
                 }
+                let duplicate = false;
+                forEachType(discriminant, t => {
+                    const id = getTypeId(getRegularTypeOfLiteralType(t));
+                    const existing = map.get(id);
+                    if (!existing) {
+                        map.set(id, type);
+                    }
+                    else if (existing !== unknownType) {
+                        map.set(id, unknownType);
+                        duplicate = true;
+                    }
+                });
+                if (!duplicate) count++;
             }
         }
         return count >= 10 && count * 2 >= types.length ? map : undefined;
diff --git a/tests/baselines/reference/missingDiscriminants2.errors.txt b/tests/baselines/reference/missingDiscriminants2.errors.txt
new file mode 100644
index 0000000000000..89852e50c4fde
--- /dev/null
+++ b/tests/baselines/reference/missingDiscriminants2.errors.txt
@@ -0,0 +1,41 @@
+missingDiscriminants2.ts(30,23): error TS2353: Object literal may only specify known properties, and 'subkind' does not exist in type '{ kind: "b"; }'.
+missingDiscriminants2.ts(31,34): error TS2353: Object literal may only specify known properties, and 'subkind' does not exist in type '{ kind: "b"; }'.
+
+
+==== missingDiscriminants2.ts (2 errors) ====
+    // https://github.com/microsoft/typescript-go/issues/1020
+    
+    type Thing =
+      | { str: "a", num: 0 }
+      | { str: "b" }
+      | { str: "c" }
+      | { str: "d" }
+      | { str: "e" }
+      | { str: "f" }
+      | { str: "g" }
+      | { str: "h" }
+      | { str: "i" }
+      | { str: "j" }
+      | { str: "k" }
+      | { str: "l" }
+      | { str: "m" }
+      | { str: "n" }
+      | { str: "o" }
+      | { num: 1 }
+    
+    const thing1: Thing = { str: "a", num: 0 }
+    const thing2: Thing = { str: "b", num: 1 } // Shouldn't be error
+    const thing3: Thing = { num: 1, str: "b" } // Shouldn't be error
+    
+    type Item =
+      | { kind: "a", subkind: 0, value: string }
+      | { kind: "a", subkind: 1, value: number }
+      | { kind: "b" }
+    
+    const item1: Item = { subkind: 1, kind: "b" } // Error, type "b" not assignable to type "a"
+                          ~~~~~~~
+!!! error TS2353: Object literal may only specify known properties, and 'subkind' does not exist in type '{ kind: "b"; }'.
+    const item2: Item = { kind: "b", subkind: 1 } // Error, 'subkind' isn't a known property
+                                     ~~~~~~~
+!!! error TS2353: Object literal may only specify known properties, and 'subkind' does not exist in type '{ kind: "b"; }'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/missingDiscriminants2.symbols b/tests/baselines/reference/missingDiscriminants2.symbols
new file mode 100644
index 0000000000000..c05c01668c2c7
--- /dev/null
+++ b/tests/baselines/reference/missingDiscriminants2.symbols
@@ -0,0 +1,103 @@
+//// [tests/cases/compiler/missingDiscriminants2.ts] ////
+
+=== missingDiscriminants2.ts ===
+// https://github.com/microsoft/typescript-go/issues/1020
+
+type Thing =
+>Thing : Symbol(Thing, Decl(missingDiscriminants2.ts, 0, 0))
+
+  | { str: "a", num: 0 }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 3, 5))
+>num : Symbol(num, Decl(missingDiscriminants2.ts, 3, 15))
+
+  | { str: "b" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 4, 5))
+
+  | { str: "c" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 5, 5))
+
+  | { str: "d" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 6, 5))
+
+  | { str: "e" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 7, 5))
+
+  | { str: "f" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 8, 5))
+
+  | { str: "g" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 9, 5))
+
+  | { str: "h" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 10, 5))
+
+  | { str: "i" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 11, 5))
+
+  | { str: "j" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 12, 5))
+
+  | { str: "k" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 13, 5))
+
+  | { str: "l" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 14, 5))
+
+  | { str: "m" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 15, 5))
+
+  | { str: "n" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 16, 5))
+
+  | { str: "o" }
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 17, 5))
+
+  | { num: 1 }
+>num : Symbol(num, Decl(missingDiscriminants2.ts, 18, 5))
+
+const thing1: Thing = { str: "a", num: 0 }
+>thing1 : Symbol(thing1, Decl(missingDiscriminants2.ts, 20, 5))
+>Thing : Symbol(Thing, Decl(missingDiscriminants2.ts, 0, 0))
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 20, 23))
+>num : Symbol(num, Decl(missingDiscriminants2.ts, 20, 33))
+
+const thing2: Thing = { str: "b", num: 1 } // Shouldn't be error
+>thing2 : Symbol(thing2, Decl(missingDiscriminants2.ts, 21, 5))
+>Thing : Symbol(Thing, Decl(missingDiscriminants2.ts, 0, 0))
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 21, 23))
+>num : Symbol(num, Decl(missingDiscriminants2.ts, 21, 33))
+
+const thing3: Thing = { num: 1, str: "b" } // Shouldn't be error
+>thing3 : Symbol(thing3, Decl(missingDiscriminants2.ts, 22, 5))
+>Thing : Symbol(Thing, Decl(missingDiscriminants2.ts, 0, 0))
+>num : Symbol(num, Decl(missingDiscriminants2.ts, 22, 23))
+>str : Symbol(str, Decl(missingDiscriminants2.ts, 22, 31))
+
+type Item =
+>Item : Symbol(Item, Decl(missingDiscriminants2.ts, 22, 42))
+
+  | { kind: "a", subkind: 0, value: string }
+>kind : Symbol(kind, Decl(missingDiscriminants2.ts, 25, 5))
+>subkind : Symbol(subkind, Decl(missingDiscriminants2.ts, 25, 16))
+>value : Symbol(value, Decl(missingDiscriminants2.ts, 25, 28))
+
+  | { kind: "a", subkind: 1, value: number }
+>kind : Symbol(kind, Decl(missingDiscriminants2.ts, 26, 5))
+>subkind : Symbol(subkind, Decl(missingDiscriminants2.ts, 26, 16))
+>value : Symbol(value, Decl(missingDiscriminants2.ts, 26, 28))
+
+  | { kind: "b" }
+>kind : Symbol(kind, Decl(missingDiscriminants2.ts, 27, 5))
+
+const item1: Item = { subkind: 1, kind: "b" } // Error, type "b" not assignable to type "a"
+>item1 : Symbol(item1, Decl(missingDiscriminants2.ts, 29, 5))
+>Item : Symbol(Item, Decl(missingDiscriminants2.ts, 22, 42))
+>subkind : Symbol(subkind, Decl(missingDiscriminants2.ts, 29, 21))
+>kind : Symbol(kind, Decl(missingDiscriminants2.ts, 29, 33))
+
+const item2: Item = { kind: "b", subkind: 1 } // Error, 'subkind' isn't a known property
+>item2 : Symbol(item2, Decl(missingDiscriminants2.ts, 30, 5))
+>Item : Symbol(Item, Decl(missingDiscriminants2.ts, 22, 42))
+>kind : Symbol(kind, Decl(missingDiscriminants2.ts, 30, 21))
+>subkind : Symbol(subkind, Decl(missingDiscriminants2.ts, 30, 32))
+
diff --git a/tests/baselines/reference/missingDiscriminants2.types b/tests/baselines/reference/missingDiscriminants2.types
new file mode 100644
index 0000000000000..10d00c873ce26
--- /dev/null
+++ b/tests/baselines/reference/missingDiscriminants2.types
@@ -0,0 +1,169 @@
+//// [tests/cases/compiler/missingDiscriminants2.ts] ////
+
+=== missingDiscriminants2.ts ===
+// https://github.com/microsoft/typescript-go/issues/1020
+
+type Thing =
+>Thing : Thing
+>      : ^^^^^
+
+  | { str: "a", num: 0 }
+>str : "a"
+>    : ^^^
+>num : 0
+>    : ^
+
+  | { str: "b" }
+>str : "b"
+>    : ^^^
+
+  | { str: "c" }
+>str : "c"
+>    : ^^^
+
+  | { str: "d" }
+>str : "d"
+>    : ^^^
+
+  | { str: "e" }
+>str : "e"
+>    : ^^^
+
+  | { str: "f" }
+>str : "f"
+>    : ^^^
+
+  | { str: "g" }
+>str : "g"
+>    : ^^^
+
+  | { str: "h" }
+>str : "h"
+>    : ^^^
+
+  | { str: "i" }
+>str : "i"
+>    : ^^^
+
+  | { str: "j" }
+>str : "j"
+>    : ^^^
+
+  | { str: "k" }
+>str : "k"
+>    : ^^^
+
+  | { str: "l" }
+>str : "l"
+>    : ^^^
+
+  | { str: "m" }
+>str : "m"
+>    : ^^^
+
+  | { str: "n" }
+>str : "n"
+>    : ^^^
+
+  | { str: "o" }
+>str : "o"
+>    : ^^^
+
+  | { num: 1 }
+>num : 1
+>    : ^
+
+const thing1: Thing = { str: "a", num: 0 }
+>thing1 : Thing
+>       : ^^^^^
+>{ str: "a", num: 0 } : { str: "a"; num: 0; }
+>                     : ^^^^^^^^^^^^^^^^^^^^^
+>str : "a"
+>    : ^^^
+>"a" : "a"
+>    : ^^^
+>num : 0
+>    : ^
+>0 : 0
+>  : ^
+
+const thing2: Thing = { str: "b", num: 1 } // Shouldn't be error
+>thing2 : Thing
+>       : ^^^^^
+>{ str: "b", num: 1 } : { str: "b"; num: 1; }
+>                     : ^^^^^^^^^^^^^^^^^^^^^
+>str : "b"
+>    : ^^^
+>"b" : "b"
+>    : ^^^
+>num : 1
+>    : ^
+>1 : 1
+>  : ^
+
+const thing3: Thing = { num: 1, str: "b" } // Shouldn't be error
+>thing3 : Thing
+>       : ^^^^^
+>{ num: 1, str: "b" } : { num: 1; str: "b"; }
+>                     : ^^^^^^^^^^^^^^^^^^^^^
+>num : 1
+>    : ^
+>1 : 1
+>  : ^
+>str : "b"
+>    : ^^^
+>"b" : "b"
+>    : ^^^
+
+type Item =
+>Item : Item
+>     : ^^^^
+
+  | { kind: "a", subkind: 0, value: string }
+>kind : "a"
+>     : ^^^
+>subkind : 0
+>        : ^
+>value : string
+>      : ^^^^^^
+
+  | { kind: "a", subkind: 1, value: number }
+>kind : "a"
+>     : ^^^
+>subkind : 1
+>        : ^
+>value : number
+>      : ^^^^^^
+
+  | { kind: "b" }
+>kind : "b"
+>     : ^^^
+
+const item1: Item = { subkind: 1, kind: "b" } // Error, type "b" not assignable to type "a"
+>item1 : Item
+>      : ^^^^
+>{ subkind: 1, kind: "b" } : { subkind: number; kind: "b"; }
+>                          : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>subkind : number
+>        : ^^^^^^
+>1 : 1
+>  : ^
+>kind : "b"
+>     : ^^^
+>"b" : "b"
+>    : ^^^
+
+const item2: Item = { kind: "b", subkind: 1 } // Error, 'subkind' isn't a known property
+>item2 : Item
+>      : ^^^^
+>{ kind: "b", subkind: 1 } : { kind: "b"; subkind: number; }
+>                          : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>kind : "b"
+>     : ^^^
+>"b" : "b"
+>    : ^^^
+>subkind : number
+>        : ^^^^^^
+>1 : 1
+>  : ^
+
diff --git a/tests/cases/compiler/missingDiscriminants2.ts b/tests/cases/compiler/missingDiscriminants2.ts
new file mode 100644
index 0000000000000..ca42b76ff2794
--- /dev/null
+++ b/tests/cases/compiler/missingDiscriminants2.ts
@@ -0,0 +1,34 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/typescript-go/issues/1020
+
+type Thing =
+  | { str: "a", num: 0 }
+  | { str: "b" }
+  | { str: "c" }
+  | { str: "d" }
+  | { str: "e" }
+  | { str: "f" }
+  | { str: "g" }
+  | { str: "h" }
+  | { str: "i" }
+  | { str: "j" }
+  | { str: "k" }
+  | { str: "l" }
+  | { str: "m" }
+  | { str: "n" }
+  | { str: "o" }
+  | { num: 1 }
+
+const thing1: Thing = { str: "a", num: 0 }
+const thing2: Thing = { str: "b", num: 1 } // Shouldn't be error
+const thing3: Thing = { num: 1, str: "b" } // Shouldn't be error
+
+type Item =
+  | { kind: "a", subkind: 0, value: string }
+  | { kind: "a", subkind: 1, value: number }
+  | { kind: "b" }
+
+const item1: Item = { subkind: 1, kind: "b" } // Error, type "b" not assignable to type "a"
+const item2: Item = { kind: "b", subkind: 1 } // Error, 'subkind' isn't a known property