diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f9ab74b053256..02d585e53bb68 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18514,10 +18514,20 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return !!(getUnionType([intersectTypes(type1, type2), neverType]).flags & TypeFlags.Never);
     }
 
+    function hasOptionalModifiersProperty(mappedType: MappedType) {
+        const modifiersType = getApparentType(getModifiersTypeFromMappedType(mappedType));
+        if (!(modifiersType.flags & TypeFlags.Object)) {
+            return false;
+        }
+        const properties = resolveStructuredTypeMembers(modifiersType as ObjectType).properties;
+        return some(properties, p => !!(p.flags & SymbolFlags.Optional));
+    }
+
     function substituteIndexedMappedType(objectType: MappedType, index: Type) {
         const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]);
         const templateMapper = combineTypeMappers(objectType.mapper, mapper);
-        return instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper);
+        const type = instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper);
+        return addOptionality(type, /*isProperty*/ true, hasOptionalModifiersProperty(objectType));
     }
 
     function getIndexedAccessType(objectType: Type, indexType: Type, accessFlags = AccessFlags.None, accessNode?: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | BindingName | SyntheticExpression, aliasSymbol?: Symbol, aliasTypeArguments?: readonly Type[]): Type {
diff --git a/tests/baselines/reference/keyofAndIndexedAccess2.errors.txt b/tests/baselines/reference/keyofAndIndexedAccess2.errors.txt
index 472421be8dca5..d0f2b5bed2a2c 100644
--- a/tests/baselines/reference/keyofAndIndexedAccess2.errors.txt
+++ b/tests/baselines/reference/keyofAndIndexedAccess2.errors.txt
@@ -31,9 +31,10 @@ keyofAndIndexedAccess2.ts(68,3): error TS2322: Type 'number' is not assignable t
   'number' is assignable to the constraint of type 'T[K]', but 'T[K]' could be instantiated with a different subtype of constraint 'number'.
 keyofAndIndexedAccess2.ts(108,5): error TS2322: Type '123' is not assignable to type 'Type[K]'.
   Type 'number' is not assignable to type 'never'.
+keyofAndIndexedAccess2.ts(115,21): error TS2313: Type parameter 'Q' has a circular constraint.
 
 
-==== keyofAndIndexedAccess2.ts (23 errors) ====
+==== keyofAndIndexedAccess2.ts (24 errors) ====
     function f1(obj: { a: number, b: 0 | 1, c: string }, k0: 'a', k1: 'a' | 'b', k2: 'a' | 'b' | 'c') {
         obj[k0] = 1;
         obj[k0] = 2;
@@ -205,6 +206,9 @@ keyofAndIndexedAccess2.ts(108,5): error TS2322: Type '123' is not assignable to
     type StrictExtract<T, U> = T extends U ? U extends T ? T : never : never;
     type StrictExclude<T, U> = T extends StrictExtract<T, U> ? never : T;
     type A<T> = { [Q in { [P in keyof T]: P; }[keyof T]]: T[Q]; };
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2313: Type parameter 'Q' has a circular constraint.
+!!! related TS2751 keyofAndIndexedAccess2.ts:116:36: Circularity originates in type at this location.
     type B<T, V> = A<{ [Q in keyof T]: StrictExclude<B<T[Q], V>, {}>; }>;
     
     // Repros from #30938