diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 34bf68b663021..0a0b50ac45ef4 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12219,9 +12219,10 @@ namespace ts {
         }
 
         function isMappedTypeGenericIndexedAccess(type: Type) {
-            return type.flags & TypeFlags.IndexedAccess && getObjectFlags((type as IndexedAccessType).objectType) & ObjectFlags.Mapped &&
-                !((type as IndexedAccessType).objectType as MappedType).declaration.nameType &&
-                !isGenericMappedType((type as IndexedAccessType).objectType) && isGenericIndexType((type as IndexedAccessType).indexType);
+            let objectType;
+            return !!(type.flags & TypeFlags.IndexedAccess && getObjectFlags(objectType = (type as IndexedAccessType).objectType) & ObjectFlags.Mapped &&
+                !isGenericMappedType(objectType) && isGenericIndexType((type as IndexedAccessType).indexType) &&
+                !(objectType as MappedType).declaration.questionToken && !(objectType as MappedType).declaration.nameType);
         }
 
         /**
diff --git a/tests/baselines/reference/correlatedUnions.js b/tests/baselines/reference/correlatedUnions.js
index f1e13f4417030..0d6698588d31c 100644
--- a/tests/baselines/reference/correlatedUnions.js
+++ b/tests/baselines/reference/correlatedUnions.js
@@ -209,6 +209,31 @@ function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
     }
     return undefined;
 }
+
+// Repro from #48157
+
+interface Foo {
+    bar?: string
+}
+
+function foo<T extends keyof Foo>(prop: T, f: Required<Foo>) {
+    bar(f[prop]);
+}
+
+declare function bar(t: string): void;
+
+// Repro from #48246
+
+declare function makeCompleteLookupMapping<T extends ReadonlyArray<any>, Attr extends keyof T[number]>(
+    ops: T, attr: Attr): { [Item in T[number]as Item[Attr]]: Item };
+
+const ALL_BARS = [{ name: 'a'}, {name: 'b'}] as const;
+
+const BAR_LOOKUP = makeCompleteLookupMapping(ALL_BARS, 'name');
+
+type BarLookup = typeof BAR_LOOKUP;
+
+type Baz = { [K in keyof BarLookup]: BarLookup[K]['name'] };
 
 
 //// [correlatedUnions.js]
@@ -325,6 +350,11 @@ function func(k) {
     }
     return undefined;
 }
+function foo(prop, f) {
+    bar(f[prop]);
+}
+var ALL_BARS = [{ name: 'a' }, { name: 'b' }];
+var BAR_LOOKUP = makeCompleteLookupMapping(ALL_BARS, 'name');
 
 
 //// [correlatedUnions.d.ts]
@@ -451,3 +481,28 @@ interface MyObj {
 }
 declare const ref: MyObj;
 declare function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined;
+interface Foo {
+    bar?: string;
+}
+declare function foo<T extends keyof Foo>(prop: T, f: Required<Foo>): void;
+declare function bar(t: string): void;
+declare function makeCompleteLookupMapping<T extends ReadonlyArray<any>, Attr extends keyof T[number]>(ops: T, attr: Attr): {
+    [Item in T[number] as Item[Attr]]: Item;
+};
+declare const ALL_BARS: readonly [{
+    readonly name: "a";
+}, {
+    readonly name: "b";
+}];
+declare const BAR_LOOKUP: {
+    a: {
+        readonly name: "a";
+    };
+    b: {
+        readonly name: "b";
+    };
+};
+declare type BarLookup = typeof BAR_LOOKUP;
+declare type Baz = {
+    [K in keyof BarLookup]: BarLookup[K]['name'];
+};
diff --git a/tests/baselines/reference/correlatedUnions.symbols b/tests/baselines/reference/correlatedUnions.symbols
index 16fa17e1a4f0e..9485b70c5dcd5 100644
--- a/tests/baselines/reference/correlatedUnions.symbols
+++ b/tests/baselines/reference/correlatedUnions.symbols
@@ -753,3 +753,74 @@ function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
 >undefined : Symbol(undefined)
 }
 
+// Repro from #48157
+
+interface Foo {
+>Foo : Symbol(Foo, Decl(correlatedUnions.ts, 209, 1))
+
+    bar?: string
+>bar : Symbol(Foo.bar, Decl(correlatedUnions.ts, 213, 15))
+}
+
+function foo<T extends keyof Foo>(prop: T, f: Required<Foo>) {
+>foo : Symbol(foo, Decl(correlatedUnions.ts, 215, 1))
+>T : Symbol(T, Decl(correlatedUnions.ts, 217, 13))
+>Foo : Symbol(Foo, Decl(correlatedUnions.ts, 209, 1))
+>prop : Symbol(prop, Decl(correlatedUnions.ts, 217, 34))
+>T : Symbol(T, Decl(correlatedUnions.ts, 217, 13))
+>f : Symbol(f, Decl(correlatedUnions.ts, 217, 42))
+>Required : Symbol(Required, Decl(lib.es5.d.ts, --, --))
+>Foo : Symbol(Foo, Decl(correlatedUnions.ts, 209, 1))
+
+    bar(f[prop]);
+>bar : Symbol(bar, Decl(correlatedUnions.ts, 219, 1))
+>f : Symbol(f, Decl(correlatedUnions.ts, 217, 42))
+>prop : Symbol(prop, Decl(correlatedUnions.ts, 217, 34))
+}
+
+declare function bar(t: string): void;
+>bar : Symbol(bar, Decl(correlatedUnions.ts, 219, 1))
+>t : Symbol(t, Decl(correlatedUnions.ts, 221, 21))
+
+// Repro from #48246
+
+declare function makeCompleteLookupMapping<T extends ReadonlyArray<any>, Attr extends keyof T[number]>(
+>makeCompleteLookupMapping : Symbol(makeCompleteLookupMapping, Decl(correlatedUnions.ts, 221, 38))
+>T : Symbol(T, Decl(correlatedUnions.ts, 225, 43))
+>ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.es5.d.ts, --, --))
+>Attr : Symbol(Attr, Decl(correlatedUnions.ts, 225, 72))
+>T : Symbol(T, Decl(correlatedUnions.ts, 225, 43))
+
+    ops: T, attr: Attr): { [Item in T[number]as Item[Attr]]: Item };
+>ops : Symbol(ops, Decl(correlatedUnions.ts, 225, 103))
+>T : Symbol(T, Decl(correlatedUnions.ts, 225, 43))
+>attr : Symbol(attr, Decl(correlatedUnions.ts, 226, 11))
+>Attr : Symbol(Attr, Decl(correlatedUnions.ts, 225, 72))
+>Item : Symbol(Item, Decl(correlatedUnions.ts, 226, 28))
+>T : Symbol(T, Decl(correlatedUnions.ts, 225, 43))
+>Item : Symbol(Item, Decl(correlatedUnions.ts, 226, 28))
+>Attr : Symbol(Attr, Decl(correlatedUnions.ts, 225, 72))
+>Item : Symbol(Item, Decl(correlatedUnions.ts, 226, 28))
+
+const ALL_BARS = [{ name: 'a'}, {name: 'b'}] as const;
+>ALL_BARS : Symbol(ALL_BARS, Decl(correlatedUnions.ts, 228, 5))
+>name : Symbol(name, Decl(correlatedUnions.ts, 228, 19))
+>name : Symbol(name, Decl(correlatedUnions.ts, 228, 33))
+>const : Symbol(const)
+
+const BAR_LOOKUP = makeCompleteLookupMapping(ALL_BARS, 'name');
+>BAR_LOOKUP : Symbol(BAR_LOOKUP, Decl(correlatedUnions.ts, 230, 5))
+>makeCompleteLookupMapping : Symbol(makeCompleteLookupMapping, Decl(correlatedUnions.ts, 221, 38))
+>ALL_BARS : Symbol(ALL_BARS, Decl(correlatedUnions.ts, 228, 5))
+
+type BarLookup = typeof BAR_LOOKUP;
+>BarLookup : Symbol(BarLookup, Decl(correlatedUnions.ts, 230, 63))
+>BAR_LOOKUP : Symbol(BAR_LOOKUP, Decl(correlatedUnions.ts, 230, 5))
+
+type Baz = { [K in keyof BarLookup]: BarLookup[K]['name'] };
+>Baz : Symbol(Baz, Decl(correlatedUnions.ts, 232, 35))
+>K : Symbol(K, Decl(correlatedUnions.ts, 234, 14))
+>BarLookup : Symbol(BarLookup, Decl(correlatedUnions.ts, 230, 63))
+>BarLookup : Symbol(BarLookup, Decl(correlatedUnions.ts, 230, 63))
+>K : Symbol(K, Decl(correlatedUnions.ts, 234, 14))
+
diff --git a/tests/baselines/reference/correlatedUnions.types b/tests/baselines/reference/correlatedUnions.types
index 3a4d950070704..ec83dd5426dfa 100644
--- a/tests/baselines/reference/correlatedUnions.types
+++ b/tests/baselines/reference/correlatedUnions.types
@@ -695,3 +695,61 @@ function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
 >undefined : undefined
 }
 
+// Repro from #48157
+
+interface Foo {
+    bar?: string
+>bar : string | undefined
+}
+
+function foo<T extends keyof Foo>(prop: T, f: Required<Foo>) {
+>foo : <T extends "bar">(prop: T, f: Required<Foo>) => void
+>prop : T
+>f : Required<Foo>
+
+    bar(f[prop]);
+>bar(f[prop]) : void
+>bar : (t: string) => void
+>f[prop] : Required<Foo>[T]
+>f : Required<Foo>
+>prop : T
+}
+
+declare function bar(t: string): void;
+>bar : (t: string) => void
+>t : string
+
+// Repro from #48246
+
+declare function makeCompleteLookupMapping<T extends ReadonlyArray<any>, Attr extends keyof T[number]>(
+>makeCompleteLookupMapping : <T extends readonly any[], Attr extends keyof T[number]>(ops: T, attr: Attr) => { [Item in T[number] as Item[Attr]]: Item; }
+
+    ops: T, attr: Attr): { [Item in T[number]as Item[Attr]]: Item };
+>ops : T
+>attr : Attr
+
+const ALL_BARS = [{ name: 'a'}, {name: 'b'}] as const;
+>ALL_BARS : readonly [{ readonly name: "a"; }, { readonly name: "b"; }]
+>[{ name: 'a'}, {name: 'b'}] as const : readonly [{ readonly name: "a"; }, { readonly name: "b"; }]
+>[{ name: 'a'}, {name: 'b'}] : readonly [{ readonly name: "a"; }, { readonly name: "b"; }]
+>{ name: 'a'} : { readonly name: "a"; }
+>name : "a"
+>'a' : "a"
+>{name: 'b'} : { readonly name: "b"; }
+>name : "b"
+>'b' : "b"
+
+const BAR_LOOKUP = makeCompleteLookupMapping(ALL_BARS, 'name');
+>BAR_LOOKUP : { a: { readonly name: "a"; }; b: { readonly name: "b"; }; }
+>makeCompleteLookupMapping(ALL_BARS, 'name') : { a: { readonly name: "a"; }; b: { readonly name: "b"; }; }
+>makeCompleteLookupMapping : <T extends readonly any[], Attr extends keyof T[number]>(ops: T, attr: Attr) => { [Item in T[number] as Item[Attr]]: Item; }
+>ALL_BARS : readonly [{ readonly name: "a"; }, { readonly name: "b"; }]
+>'name' : "name"
+
+type BarLookup = typeof BAR_LOOKUP;
+>BarLookup : { a: { readonly name: "a"; }; b: { readonly name: "b"; }; }
+>BAR_LOOKUP : { a: { readonly name: "a"; }; b: { readonly name: "b"; }; }
+
+type Baz = { [K in keyof BarLookup]: BarLookup[K]['name'] };
+>Baz : Baz
+
diff --git a/tests/cases/compiler/correlatedUnions.ts b/tests/cases/compiler/correlatedUnions.ts
index f6b4086f03f5a..e75e56f15ce69 100644
--- a/tests/cases/compiler/correlatedUnions.ts
+++ b/tests/cases/compiler/correlatedUnions.ts
@@ -211,3 +211,28 @@ function func<K extends keyof MyObj>(k: K): MyObj[K]['name'] | undefined {
     }
     return undefined;
 }
+
+// Repro from #48157
+
+interface Foo {
+    bar?: string
+}
+
+function foo<T extends keyof Foo>(prop: T, f: Required<Foo>) {
+    bar(f[prop]);
+}
+
+declare function bar(t: string): void;
+
+// Repro from #48246
+
+declare function makeCompleteLookupMapping<T extends ReadonlyArray<any>, Attr extends keyof T[number]>(
+    ops: T, attr: Attr): { [Item in T[number]as Item[Attr]]: Item };
+
+const ALL_BARS = [{ name: 'a'}, {name: 'b'}] as const;
+
+const BAR_LOOKUP = makeCompleteLookupMapping(ALL_BARS, 'name');
+
+type BarLookup = typeof BAR_LOOKUP;
+
+type Baz = { [K in keyof BarLookup]: BarLookup[K]['name'] };