diff --git a/tests/baselines/reference/callChain.types b/tests/baselines/reference/callChain.types
index 1f1a4f1b7c9..ea4700aa957 100644
--- a/tests/baselines/reference/callChain.types
+++ b/tests/baselines/reference/callChain.types
@@ -260,7 +260,7 @@ declare const o5: <T>() => undefined | (() => void);
 >o5 : <T>() => undefined | (() => void)
 
 o5<number>()?.();
->o5<number>()?.() : void
+>o5<number>()?.() : void | undefined
 >o5<number>() : (() => void) | undefined
 >o5 : <T>() => (() => void) | undefined
 
diff --git a/tests/baselines/reference/callChainInference.types b/tests/baselines/reference/callChainInference.types
index 3f19f66091e..4ed4f5acf6e 100644
--- a/tests/baselines/reference/callChainInference.types
+++ b/tests/baselines/reference/callChainInference.types
@@ -29,7 +29,7 @@ if (value) {
 }
 
 value?.foo("a");
->value?.foo("a") : void
+>value?.foo("a") : void | undefined
 >value?.foo : (<T>(this: T, arg: keyof T) => void) | undefined
 >value : Y | undefined
 >foo : (<T>(this: T, arg: keyof T) => void) | undefined
diff --git a/tests/baselines/reference/controlFlowOptionalChain.types b/tests/baselines/reference/controlFlowOptionalChain.types
index 78be0e6f295..4e335fca6d2 100644
--- a/tests/baselines/reference/controlFlowOptionalChain.types
+++ b/tests/baselines/reference/controlFlowOptionalChain.types
@@ -595,7 +595,7 @@ function f01(x: unknown) {
 >true : true
 
         maybeIsString?.(x);
->maybeIsString?.(x) : void
+>maybeIsString?.(x) : void | undefined
 >maybeIsString : ((value: unknown) => asserts value is string) | undefined
 >x : unknown
 
diff --git a/tests/baselines/reference/controlFlowSuperPropertyAccess.types b/tests/baselines/reference/controlFlowSuperPropertyAccess.types
index 82ba6ccd34e..87e7b3f00d0 100644
--- a/tests/baselines/reference/controlFlowSuperPropertyAccess.types
+++ b/tests/baselines/reference/controlFlowSuperPropertyAccess.types
@@ -13,7 +13,7 @@ class C extends B {
 >body : () => void
 
         super.m && super.m();
->super.m && super.m() : void
+>super.m && super.m() : void | undefined
 >super.m : (() => void) | undefined
 >super : B
 >m : (() => void) | undefined
diff --git a/tests/baselines/reference/discriminantPropertyCheck.types b/tests/baselines/reference/discriminantPropertyCheck.types
index 38e04bf6a04..10d3b5f117c 100644
--- a/tests/baselines/reference/discriminantPropertyCheck.types
+++ b/tests/baselines/reference/discriminantPropertyCheck.types
@@ -343,7 +343,7 @@ const u: U = {} as any;
 >{} : {}
 
 u.a && u.b && f(u.a, u.b);
->u.a && u.b && f(u.a, u.b) : void | ""
+>u.a && u.b && f(u.a, u.b) : void | "" | undefined
 >u.a && u.b : string | undefined
 >u.a : string | undefined
 >u : U
@@ -361,7 +361,7 @@ u.a && u.b && f(u.a, u.b);
 >b : string
 
 u.b && u.a && f(u.a, u.b);
->u.b && u.a && f(u.a, u.b) : void | ""
+>u.b && u.a && f(u.a, u.b) : void | "" | undefined
 >u.b && u.a : string | undefined
 >u.b : string | undefined
 >u : U
diff --git a/tests/baselines/reference/promiseTypeStrictNull.types b/tests/baselines/reference/promiseTypeStrictNull.types
index 5e27b4ccd76..97038aeb4e5 100644
--- a/tests/baselines/reference/promiseTypeStrictNull.types
+++ b/tests/baselines/reference/promiseTypeStrictNull.types
@@ -888,8 +888,8 @@ const p75 = p.then(() => undefined, () => null);
 >null : null
 
 const p76 = p.then(() => undefined, () => {});
->p76 : Promise<void>
->p.then(() => undefined, () => {}) : Promise<void>
+>p76 : Promise<void | undefined>
+>p.then(() => undefined, () => {}) : Promise<void | undefined>
 >p.then : <TResult1 = boolean, TResult2 = never>(onfulfilled?: ((value: boolean) => TResult1 | PromiseLike<TResult1>) | null | undefined, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined) => Promise<TResult1 | TResult2>
 >p : Promise<boolean>
 >then : <TResult1 = boolean, TResult2 = never>(onfulfilled?: ((value: boolean) => TResult1 | PromiseLike<TResult1>) | null | undefined, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined) => Promise<TResult1 | TResult2>
@@ -1092,8 +1092,8 @@ const p93 = p.then(() => {}, () => x);
 >x : any
 
 const p94 = p.then(() => {}, () => undefined);
->p94 : Promise<void>
->p.then(() => {}, () => undefined) : Promise<void>
+>p94 : Promise<void | undefined>
+>p.then(() => {}, () => undefined) : Promise<void | undefined>
 >p.then : <TResult1 = boolean, TResult2 = never>(onfulfilled?: ((value: boolean) => TResult1 | PromiseLike<TResult1>) | null | undefined, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined) => Promise<TResult1 | TResult2>
 >p : Promise<boolean>
 >then : <TResult1 = boolean, TResult2 = never>(onfulfilled?: ((value: boolean) => TResult1 | PromiseLike<TResult1>) | null | undefined, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined) => Promise<TResult1 | TResult2>
diff --git a/tests/baselines/reference/superMethodCall.types b/tests/baselines/reference/superMethodCall.types
index 7f81a8d7adf..16d40d19ded 100644
--- a/tests/baselines/reference/superMethodCall.types
+++ b/tests/baselines/reference/superMethodCall.types
@@ -11,20 +11,20 @@ class Derived extends Base {
 >Base : Base
 
     method() {
->method : () => void
+>method : () => void | undefined
 
         return super.method?.();
->super.method?.() : void
+>super.method?.() : void | undefined
 >super.method : (() => void) | undefined
 >super : Base
 >method : (() => void) | undefined
     }
 
     async asyncMethod() {
->asyncMethod : () => Promise<void>
+>asyncMethod : () => Promise<void | undefined>
 
         return super.method?.();
->super.method?.() : void
+>super.method?.() : void | undefined
 >super.method : (() => void) | undefined
 >super : Base
 >method : (() => void) | undefined
diff --git a/tests/baselines/reference/thisMethodCall.types b/tests/baselines/reference/thisMethodCall.types
index b00d50fe4f4..08e023a44d2 100644
--- a/tests/baselines/reference/thisMethodCall.types
+++ b/tests/baselines/reference/thisMethodCall.types
@@ -9,7 +9,7 @@ class C {
 >other : () => void
 
         this.method?.();
->this.method?.() : void
+>this.method?.() : void | undefined
 >this.method : (() => void) | undefined
 >this : this
 >method : (() => void) | undefined
diff --git a/tests/baselines/reference/truthinessCallExpressionCoercion2.types b/tests/baselines/reference/truthinessCallExpressionCoercion2.types
index d8b79c8318f..83c867e6f8e 100644
--- a/tests/baselines/reference/truthinessCallExpressionCoercion2.types
+++ b/tests/baselines/reference/truthinessCallExpressionCoercion2.types
@@ -60,7 +60,7 @@ function test(required1: () => boolean, required2: () => boolean, b: boolean, op
 
     // ok
     optional && console.log('optional');
->optional && console.log('optional') : void
+>optional && console.log('optional') : void | undefined
 >optional : (() => boolean) | undefined
 >console.log('optional') : void
 >console.log : (...data: any[]) => void
@@ -70,7 +70,7 @@ function test(required1: () => boolean, required2: () => boolean, b: boolean, op
 
     // ok
     1 && optional && console.log('optional');
->1 && optional && console.log('optional') : void
+>1 && optional && console.log('optional') : void | undefined
 >1 && optional : (() => boolean) | undefined
 >1 : 1
 >optional : (() => boolean) | undefined
@@ -441,7 +441,7 @@ class Foo {
 
         // ok
         1 && this.optional && console.log('optional');
->1 && this.optional && console.log('optional') : void
+>1 && this.optional && console.log('optional') : void | undefined
 >1 && this.optional : (() => boolean) | undefined
 >1 : 1
 >this.optional : (() => boolean) | undefined
diff --git a/tests/baselines/reference/typeVariableTypeGuards.types b/tests/baselines/reference/typeVariableTypeGuards.types
index 35656ad71d6..063f6bbc96d 100644
--- a/tests/baselines/reference/typeVariableTypeGuards.types
+++ b/tests/baselines/reference/typeVariableTypeGuards.types
@@ -16,7 +16,7 @@ class A<P extends Partial<Foo>> {
 >doSomething : () => void
 
         this.props.foo && this.props.foo()
->this.props.foo && this.props.foo() : void
+>this.props.foo && this.props.foo() : void | undefined
 >this.props.foo : P["foo"] | undefined
 >this.props : Readonly<P>
 >this : this
diff --git a/tests/baselines/reference/voidReturnIndexUnionInference.types b/tests/baselines/reference/voidReturnIndexUnionInference.types
index 14986116433..fa7d87b8f63 100644
--- a/tests/baselines/reference/voidReturnIndexUnionInference.types
+++ b/tests/baselines/reference/voidReturnIndexUnionInference.types
@@ -51,7 +51,7 @@ function bad<P extends Props>(props: Readonly<P>) {
     // ERROR HERE!!!
     // Type R in signature of safeInvoke incorrectly inferred as {} instead of void!
     safeInvoke(props.onBar, "blah");
->safeInvoke(props.onBar, "blah") : void
+>safeInvoke(props.onBar, "blah") : void | undefined
 >safeInvoke : <A1, R>(func: ((arg1: A1) => R) | null | undefined, arg1: A1) => R | undefined
 >props.onBar : P["onBar"] | undefined
 >props : Readonly<P>