diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 07801f5b5bc92..908e2ce665d95 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8109,12 +8109,16 @@ namespace ts {
             return links.resolvedType;
         }
 
-        function getIndexTypeForGenericType(type: InstantiableType | UnionOrIntersectionType) {
-            if (!type.resolvedIndexType) {
-                type.resolvedIndexType = <IndexType>createType(TypeFlags.Index);
-                type.resolvedIndexType.type = type;
+        function getIndexTypeForGenericType(type: InstantiableType | UnionOrIntersectionType, includeDeclaredTypes?: boolean) {
+            const cacheLocation = includeDeclaredTypes ? "resolvedDeclaredIndexType" : "resolvedIndexType";
+            if (!type[cacheLocation]) {
+                type[cacheLocation] = <IndexType>createType(TypeFlags.Index);
+                type[cacheLocation].type = type;
+                if (includeDeclaredTypes) {
+                    type[cacheLocation].isDeclaredType = true;
+                }
             }
-            return type.resolvedIndexType;
+            return type[cacheLocation];
         }
 
         function getLiteralTypeFromPropertyName(prop: Symbol) {
@@ -8132,17 +8136,22 @@ namespace ts {
             return links.nameType;
         }
 
-        function getLiteralTypeFromPropertyNames(type: Type) {
-            return getUnionType(map(getPropertiesOfType(type), getLiteralTypeFromPropertyName));
+        function isTypeString(type: Type) {
+            return isTypeAssignableToKind(type, TypeFlags.StringLike);
+        }
+
+        function getLiteralTypeFromPropertyNames(type: Type, includeDeclaredTypes?: boolean) {
+            const originalKeys = map(getPropertiesOfType(type), getLiteralTypeFromPropertyName);
+            return getUnionType(includeDeclaredTypes ? originalKeys : filter(originalKeys, isTypeString));
         }
 
-        function getIndexType(type: Type): Type {
-            return type.flags & TypeFlags.Intersection ? getUnionType(map((<IntersectionType>type).types, t => getIndexType(t))) :
-                maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive) ? getIndexTypeForGenericType(<InstantiableType | UnionOrIntersectionType>type) :
+        function getIndexType(type: Type, includeDeclaredTypes?: boolean): Type {
+            return type.flags & TypeFlags.Intersection ? getUnionType(map((<IntersectionType>type).types, t => getIndexType(t, includeDeclaredTypes))) :
+                maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive) ? getIndexTypeForGenericType(<InstantiableType | UnionOrIntersectionType>type, includeDeclaredTypes) :
                 getObjectFlags(type) & ObjectFlags.Mapped ? getConstraintTypeFromMappedType(<MappedType>type) :
                 type === wildcardType ? wildcardType :
                 type.flags & TypeFlags.Any || getIndexInfoOfType(type, IndexKind.String) ? stringType :
-                getLiteralTypeFromPropertyNames(type);
+                getLiteralTypeFromPropertyNames(type, includeDeclaredTypes);
         }
 
         function getIndexTypeOrString(type: Type): Type {
@@ -10318,7 +10327,7 @@ namespace ts {
                     // constraint of T.
                     const constraint = getConstraintForRelation((<IndexType>target).type);
                     if (constraint) {
-                        if (result = isRelatedTo(source, getIndexType(constraint), reportErrors)) {
+                        if (result = isRelatedTo(source, getIndexType(constraint, (target as IndexType).isDeclaredType), reportErrors)) {
                             return result;
                         }
                     }
@@ -20840,7 +20849,7 @@ namespace ts {
             // Check if the index type is assignable to 'keyof T' for the object type.
             const objectType = (<IndexedAccessType>type).objectType;
             const indexType = (<IndexedAccessType>type).indexType;
-            if (isTypeAssignableTo(indexType, getIndexType(objectType))) {
+            if (isTypeAssignableTo(indexType, getIndexType(objectType, /*includeDeclaredTypes*/ true))) {
                 if (accessNode.kind === SyntaxKind.ElementAccessExpression && isAssignmentTarget(accessNode) &&
                     getObjectFlags(objectType) & ObjectFlags.Mapped && getMappedTypeModifiers(<MappedType>objectType) & MappedTypeModifiers.IncludeReadonly) {
                     error(accessNode, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(objectType));
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 63829b0fa9aef..a526ecc5dff98 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3753,6 +3753,8 @@ namespace ts {
         /* @internal */
         resolvedIndexType: IndexType;
         /* @internal */
+        resolvedDeclaredIndexType: IndexType;
+        /* @internal */
         resolvedBaseConstraint: Type;
         /* @internal */
         couldContainTypeVariables: boolean;
@@ -3839,6 +3841,8 @@ namespace ts {
         resolvedBaseConstraint?: Type;
         /* @internal */
         resolvedIndexType?: IndexType;
+        /* @internal */
+        resolvedDeclaredIndexType?: IndexType;
     }
 
     // Type parameters (TypeFlags.TypeParameter)
@@ -3870,6 +3874,8 @@ namespace ts {
 
     // keyof T types (TypeFlags.Index)
     export interface IndexType extends InstantiableType {
+        /* @internal */
+        isDeclaredType?: boolean;
         type: InstantiableType | UnionOrIntersectionType;
     }
 
diff --git a/tests/baselines/reference/keyofDoesntContainSymbols.errors.txt b/tests/baselines/reference/keyofDoesntContainSymbols.errors.txt
new file mode 100644
index 0000000000000..f87631f9dbae1
--- /dev/null
+++ b/tests/baselines/reference/keyofDoesntContainSymbols.errors.txt
@@ -0,0 +1,36 @@
+tests/cases/compiler/keyofDoesntContainSymbols.ts(11,30): error TS2345: Argument of type '""' is not assignable to parameter of type 'number'.
+tests/cases/compiler/keyofDoesntContainSymbols.ts(14,23): error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"str" | "num"'.
+tests/cases/compiler/keyofDoesntContainSymbols.ts(17,23): error TS2345: Argument of type '0' is not assignable to parameter of type '"str" | "num"'.
+
+
+==== tests/cases/compiler/keyofDoesntContainSymbols.ts (3 errors) ====
+    const sym = Symbol();
+    const num = 0;
+    const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
+    
+    function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
+      return obj[key] = value;
+    }
+    
+    const val = set(obj, 'str', '');
+    // string
+    const valB = set(obj, 'num', '');
+                                 ~~
+!!! error TS2345: Argument of type '""' is not assignable to parameter of type 'number'.
+    // Expect type error
+    // Argument of type '""' is not assignable to parameter of type 'number'.
+    const valC = set(obj, sym, sym);
+                          ~~~
+!!! error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"str" | "num"'.
+    // Expect type error
+    // Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+    const valD = set(obj, num, num);
+                          ~~~
+!!! error TS2345: Argument of type '0' is not assignable to parameter of type '"str" | "num"'.
+    // Expect type error
+    // Argument of type '0' is not assignable to parameter of type "str" | "num"
+    type KeyofObj = keyof typeof obj;
+    // "str" | "num"
+    type Values<T> = T[keyof T];
+    
+    type ValuesOfObj = Values<typeof obj>;
\ No newline at end of file
diff --git a/tests/baselines/reference/keyofDoesntContainSymbols.js b/tests/baselines/reference/keyofDoesntContainSymbols.js
new file mode 100644
index 0000000000000..ad965aae1e4a5
--- /dev/null
+++ b/tests/baselines/reference/keyofDoesntContainSymbols.js
@@ -0,0 +1,43 @@
+//// [keyofDoesntContainSymbols.ts]
+const sym = Symbol();
+const num = 0;
+const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
+
+function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
+  return obj[key] = value;
+}
+
+const val = set(obj, 'str', '');
+// string
+const valB = set(obj, 'num', '');
+// Expect type error
+// Argument of type '""' is not assignable to parameter of type 'number'.
+const valC = set(obj, sym, sym);
+// Expect type error
+// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+const valD = set(obj, num, num);
+// Expect type error
+// Argument of type '0' is not assignable to parameter of type "str" | "num"
+type KeyofObj = keyof typeof obj;
+// "str" | "num"
+type Values<T> = T[keyof T];
+
+type ValuesOfObj = Values<typeof obj>;
+
+//// [keyofDoesntContainSymbols.js]
+var sym = Symbol();
+var num = 0;
+var obj = (_a = { num: 0, str: 's' }, _a[num] = num, _a[sym] = sym, _a);
+function set(obj, key, value) {
+    return obj[key] = value;
+}
+var val = set(obj, 'str', '');
+// string
+var valB = set(obj, 'num', '');
+// Expect type error
+// Argument of type '""' is not assignable to parameter of type 'number'.
+var valC = set(obj, sym, sym);
+// Expect type error
+// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+var valD = set(obj, num, num);
+var _a;
diff --git a/tests/baselines/reference/keyofDoesntContainSymbols.symbols b/tests/baselines/reference/keyofDoesntContainSymbols.symbols
new file mode 100644
index 0000000000000..31f208f40631f
--- /dev/null
+++ b/tests/baselines/reference/keyofDoesntContainSymbols.symbols
@@ -0,0 +1,87 @@
+=== tests/cases/compiler/keyofDoesntContainSymbols.ts ===
+const sym = Symbol();
+>sym : Symbol(sym, Decl(keyofDoesntContainSymbols.ts, 0, 5))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+
+const num = 0;
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 1, 5))
+
+const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 2, 13))
+>str : Symbol(str, Decl(keyofDoesntContainSymbols.ts, 2, 21))
+>[num] : Symbol([num], Decl(keyofDoesntContainSymbols.ts, 2, 31))
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 1, 5))
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 1, 5))
+>[sym] : Symbol([sym], Decl(keyofDoesntContainSymbols.ts, 2, 48))
+>sym : Symbol(sym, Decl(keyofDoesntContainSymbols.ts, 0, 5))
+>sym : Symbol(sym, Decl(keyofDoesntContainSymbols.ts, 0, 5))
+
+function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
+>set : Symbol(set, Decl(keyofDoesntContainSymbols.ts, 2, 62))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 4, 14))
+>K : Symbol(K, Decl(keyofDoesntContainSymbols.ts, 4, 31))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 4, 14))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 4, 52))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 4, 14))
+>key : Symbol(key, Decl(keyofDoesntContainSymbols.ts, 4, 59))
+>K : Symbol(K, Decl(keyofDoesntContainSymbols.ts, 4, 31))
+>value : Symbol(value, Decl(keyofDoesntContainSymbols.ts, 4, 67))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 4, 14))
+>K : Symbol(K, Decl(keyofDoesntContainSymbols.ts, 4, 31))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 4, 14))
+>K : Symbol(K, Decl(keyofDoesntContainSymbols.ts, 4, 31))
+
+  return obj[key] = value;
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 4, 52))
+>key : Symbol(key, Decl(keyofDoesntContainSymbols.ts, 4, 59))
+>value : Symbol(value, Decl(keyofDoesntContainSymbols.ts, 4, 67))
+}
+
+const val = set(obj, 'str', '');
+>val : Symbol(val, Decl(keyofDoesntContainSymbols.ts, 8, 5))
+>set : Symbol(set, Decl(keyofDoesntContainSymbols.ts, 2, 62))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+
+// string
+const valB = set(obj, 'num', '');
+>valB : Symbol(valB, Decl(keyofDoesntContainSymbols.ts, 10, 5))
+>set : Symbol(set, Decl(keyofDoesntContainSymbols.ts, 2, 62))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+
+// Expect type error
+// Argument of type '""' is not assignable to parameter of type 'number'.
+const valC = set(obj, sym, sym);
+>valC : Symbol(valC, Decl(keyofDoesntContainSymbols.ts, 13, 5))
+>set : Symbol(set, Decl(keyofDoesntContainSymbols.ts, 2, 62))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+>sym : Symbol(sym, Decl(keyofDoesntContainSymbols.ts, 0, 5))
+>sym : Symbol(sym, Decl(keyofDoesntContainSymbols.ts, 0, 5))
+
+// Expect type error
+// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+const valD = set(obj, num, num);
+>valD : Symbol(valD, Decl(keyofDoesntContainSymbols.ts, 16, 5))
+>set : Symbol(set, Decl(keyofDoesntContainSymbols.ts, 2, 62))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 1, 5))
+>num : Symbol(num, Decl(keyofDoesntContainSymbols.ts, 1, 5))
+
+// Expect type error
+// Argument of type '0' is not assignable to parameter of type "str" | "num"
+type KeyofObj = keyof typeof obj;
+>KeyofObj : Symbol(KeyofObj, Decl(keyofDoesntContainSymbols.ts, 16, 32))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+
+// "str" | "num"
+type Values<T> = T[keyof T];
+>Values : Symbol(Values, Decl(keyofDoesntContainSymbols.ts, 19, 33))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 21, 12))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 21, 12))
+>T : Symbol(T, Decl(keyofDoesntContainSymbols.ts, 21, 12))
+
+type ValuesOfObj = Values<typeof obj>;
+>ValuesOfObj : Symbol(ValuesOfObj, Decl(keyofDoesntContainSymbols.ts, 21, 28))
+>Values : Symbol(Values, Decl(keyofDoesntContainSymbols.ts, 19, 33))
+>obj : Symbol(obj, Decl(keyofDoesntContainSymbols.ts, 2, 5))
+
diff --git a/tests/baselines/reference/keyofDoesntContainSymbols.types b/tests/baselines/reference/keyofDoesntContainSymbols.types
new file mode 100644
index 0000000000000..e07f6a234c13e
--- /dev/null
+++ b/tests/baselines/reference/keyofDoesntContainSymbols.types
@@ -0,0 +1,103 @@
+=== tests/cases/compiler/keyofDoesntContainSymbols.ts ===
+const sym = Symbol();
+>sym : unique symbol
+>Symbol() : unique symbol
+>Symbol : SymbolConstructor
+
+const num = 0;
+>num : 0
+>0 : 0
+
+const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>{ num: 0, str: 's', [num]: num as 0, [sym]: sym } : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>num : number
+>0 : 0
+>str : string
+>'s' : "s"
+>[num] : 0
+>num : 0
+>num as 0 : 0
+>num : 0
+>[sym] : symbol
+>sym : unique symbol
+>sym : unique symbol
+
+function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
+>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
+>T : T
+>K : K
+>T : T
+>obj : T
+>T : T
+>key : K
+>K : K
+>value : T[K]
+>T : T
+>K : K
+>T : T
+>K : K
+
+  return obj[key] = value;
+>obj[key] = value : T[K]
+>obj[key] : T[K]
+>obj : T
+>key : K
+>value : T[K]
+}
+
+const val = set(obj, 'str', '');
+>val : string
+>set(obj, 'str', '') : string
+>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>'str' : "str"
+>'' : ""
+
+// string
+const valB = set(obj, 'num', '');
+>valB : any
+>set(obj, 'num', '') : any
+>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>'num' : "num"
+>'' : ""
+
+// Expect type error
+// Argument of type '""' is not assignable to parameter of type 'number'.
+const valC = set(obj, sym, sym);
+>valC : any
+>set(obj, sym, sym) : any
+>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>sym : unique symbol
+>sym : unique symbol
+
+// Expect type error
+// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+const valD = set(obj, num, num);
+>valD : any
+>set(obj, num, num) : any
+>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+>num : 0
+>num : 0
+
+// Expect type error
+// Argument of type '0' is not assignable to parameter of type "str" | "num"
+type KeyofObj = keyof typeof obj;
+>KeyofObj : "str" | "num"
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+
+// "str" | "num"
+type Values<T> = T[keyof T];
+>Values : T[keyof T]
+>T : T
+>T : T
+>T : T
+
+type ValuesOfObj = Values<typeof obj>;
+>ValuesOfObj : string | number
+>Values : T[keyof T]
+>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
+
diff --git a/tests/cases/compiler/keyofDoesntContainSymbols.ts b/tests/cases/compiler/keyofDoesntContainSymbols.ts
new file mode 100644
index 0000000000000..5690d4c6b8825
--- /dev/null
+++ b/tests/cases/compiler/keyofDoesntContainSymbols.ts
@@ -0,0 +1,25 @@
+// @lib: es6
+const sym = Symbol();
+const num = 0;
+const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
+
+function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
+  return obj[key] = value;
+}
+
+const val = set(obj, 'str', '');
+// string
+const valB = set(obj, 'num', '');
+// Expect type error
+// Argument of type '""' is not assignable to parameter of type 'number'.
+const valC = set(obj, sym, sym);
+// Expect type error
+// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
+const valD = set(obj, num, num);
+// Expect type error
+// Argument of type '0' is not assignable to parameter of type "str" | "num"
+type KeyofObj = keyof typeof obj;
+// "str" | "num"
+type Values<T> = T[keyof T];
+
+type ValuesOfObj = Values<typeof obj>;
\ No newline at end of file