diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index edefd6bf9dde5..caa75a45eb987 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -892,6 +892,7 @@ namespace ts {
         function mergeSymbol(target: Symbol, source: Symbol) {
             if (!(target.flags & getExcludedSymbolFlags(source.flags)) ||
                 (source.flags | target.flags) & SymbolFlags.JSContainer) {
+                Debug.assert(!!(target.flags & SymbolFlags.Transient));
                 // Javascript static-property-assignment declarations always merge, even though they are also values
                 if (source.flags & SymbolFlags.ValueModule && target.flags & SymbolFlags.ValueModule && target.constEnumOnlyModule && !source.constEnumOnlyModule) {
                     // reset flag when merging instantiated module into value module that has only const enums
@@ -915,8 +916,12 @@ namespace ts {
                 }
                 if ((source.flags | target.flags) & SymbolFlags.JSContainer) {
                     const sourceInitializer = getJSInitializerSymbol(source);
-                    const targetInitializer = getJSInitializerSymbol(target);
+                    let targetInitializer = getJSInitializerSymbol(target);
                     if (sourceInitializer !== source || targetInitializer !== target) {
+                        if (!(targetInitializer.flags & SymbolFlags.Transient)) {
+                            const mergedInitializer = getMergedSymbol(targetInitializer);
+                            targetInitializer = mergedInitializer === targetInitializer ? cloneSymbol(targetInitializer) : mergedInitializer;
+                        }
                         mergeSymbol(targetInitializer, sourceInitializer);
                     }
                 }
@@ -19452,7 +19457,7 @@ namespace ts {
             }
 
             const links = getNodeLinks(node);
-            const type = getTypeOfSymbol(node.symbol);
+            const type = getTypeOfSymbol(getMergedSymbol(node.symbol));
             if (isTypeAny(type)) {
                 return type;
             }
diff --git a/tests/baselines/reference/typeFromPropertyAssignment10.types b/tests/baselines/reference/typeFromPropertyAssignment10.types
index f4d118165373e..a880498f047c7 100644
--- a/tests/baselines/reference/typeFromPropertyAssignment10.types
+++ b/tests/baselines/reference/typeFromPropertyAssignment10.types
@@ -1,28 +1,28 @@
 === tests/cases/conformance/salsa/module.js ===
 var Outer = Outer || {};
->Outer : typeof __object
->Outer || {} : typeof __object
->Outer : typeof __object
->{} : typeof __object
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>Outer || {} : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>{} : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
 
 Outer.app = Outer.app || {};
->Outer.app = Outer.app || {} : typeof __object
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
->Outer.app || {} : typeof __object
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
->{} : typeof __object
+>Outer.app = Outer.app || {} : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer.app || {} : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>{} : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 
 === tests/cases/conformance/salsa/someview.js ===
 Outer.app.SomeView = (function () {
 >Outer.app.SomeView = (function () {    var SomeView = function() {        var me = this;    }    return SomeView;})() : () => void
 >Outer.app.SomeView : () => void
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >SomeView : () => void
 >(function () {    var SomeView = function() {        var me = this;    }    return SomeView;})() : () => void
 >(function () {    var SomeView = function() {        var me = this;    }    return SomeView;}) : () => () => void
@@ -43,9 +43,9 @@ Outer.app.SomeView = (function () {
 Outer.app.Inner = class {
 >Outer.app.Inner = class {    constructor() {        /** @type {number} */        this.y = 12;    }} : typeof Inner
 >Outer.app.Inner : typeof Inner
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >Inner : typeof Inner
 >class {    constructor() {        /** @type {number} */        this.y = 12;    }} : typeof Inner
 
@@ -63,9 +63,9 @@ var example = new Outer.app.Inner();
 >example : Inner
 >new Outer.app.Inner() : Inner
 >Outer.app.Inner : typeof Inner
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >Inner : typeof Inner
 
 example.y;
@@ -77,9 +77,9 @@ example.y;
 Outer.app.statische = function (k) {
 >Outer.app.statische = function (k) {    return k ** k;} : (k: number) => number
 >Outer.app.statische : (k: number) => number
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >statische : (k: number) => number
 >function (k) {    return k ** k;} : (k: number) => number
 >k : number
@@ -93,9 +93,9 @@ Outer.app.statische = function (k) {
 Outer.app.Application = (function () {
 >Outer.app.Application = (function () {    /**     * Application main class.     * Will be instantiated & initialized by HTML page     */    var Application = function () {        var me = this;        me.view = new Outer.app.SomeView();    };    return Application;})() : () => void
 >Outer.app.Application : () => void
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >Application : () => void
 >(function () {    /**     * Application main class.     * Will be instantiated & initialized by HTML page     */    var Application = function () {        var me = this;        me.view = new Outer.app.SomeView();    };    return Application;})() : () => void
 >(function () {    /**     * Application main class.     * Will be instantiated & initialized by HTML page     */    var Application = function () {        var me = this;        me.view = new Outer.app.SomeView();    };    return Application;}) : () => () => void
@@ -120,9 +120,9 @@ Outer.app.Application = (function () {
 >view : any
 >new Outer.app.SomeView() : any
 >Outer.app.SomeView : () => void
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >SomeView : () => void
 
     };
@@ -135,18 +135,18 @@ var app = new Outer.app.Application();
 >app : any
 >new Outer.app.Application() : any
 >Outer.app.Application : () => void
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >Application : () => void
 
 var inner = new Outer.app.Inner();
 >inner : Inner
 >new Outer.app.Inner() : Inner
 >Outer.app.Inner : typeof Inner
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >Inner : typeof Inner
 
 inner.y;
@@ -166,9 +166,9 @@ x.y;
 Outer.app.statische(101); // Infinity, duh
 >Outer.app.statische(101) : number
 >Outer.app.statische : (k: number) => number
->Outer.app : typeof __object
->Outer : typeof __object
->app : typeof __object
+>Outer.app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
+>Outer : { [x: string]: any; app: { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }; }
+>app : { [x: string]: any; SomeView: () => void; Inner: typeof Inner; statische(k: number): number; Application: () => void; }
 >statische : (k: number) => number
 >101 : 101
 
diff --git a/tests/baselines/reference/typeFromPropertyAssignment14.types b/tests/baselines/reference/typeFromPropertyAssignment14.types
index 10a3fa00e3514..0416d2de952fe 100644
--- a/tests/baselines/reference/typeFromPropertyAssignment14.types
+++ b/tests/baselines/reference/typeFromPropertyAssignment14.types
@@ -1,13 +1,13 @@
 === tests/cases/conformance/salsa/def.js ===
 var Outer = {};
->Outer : typeof Outer
->{} : typeof Outer
+>Outer : { [x: string]: any; Inner(): void; }
+>{} : { [x: string]: any; Inner(): void; }
 
 === tests/cases/conformance/salsa/work.js ===
 Outer.Inner = function () {}
 >Outer.Inner = function () {} : () => void
 >Outer.Inner : () => void
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner(): void; }
 >Inner : () => void
 >function () {} : () => void
 
@@ -15,7 +15,7 @@ Outer.Inner.prototype = {
 >Outer.Inner.prototype = {    x: 1,    m() { }} : { [x: string]: any; x: number; m(): void; }
 >Outer.Inner.prototype : any
 >Outer.Inner : () => void
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner(): void; }
 >Inner : () => void
 >prototype : any
 >{    x: 1,    m() { }} : { [x: string]: any; x: number; m(): void; }
@@ -48,7 +48,7 @@ var inno = new Outer.Inner()
 >inno : { [x: string]: any; x: number; m(): void; }
 >new Outer.Inner() : { [x: string]: any; x: number; m(): void; }
 >Outer.Inner : () => void
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner(): void; }
 >Inner : () => void
 
 inno.x
diff --git a/tests/baselines/reference/typeFromPropertyAssignment4.types b/tests/baselines/reference/typeFromPropertyAssignment4.types
index 3b46296c10e94..90b97d91d0c32 100644
--- a/tests/baselines/reference/typeFromPropertyAssignment4.types
+++ b/tests/baselines/reference/typeFromPropertyAssignment4.types
@@ -1,13 +1,13 @@
 === tests/cases/conformance/salsa/def.js ===
 var Outer = {};
->Outer : typeof Outer
->{} : typeof Outer
+>Outer : { [x: string]: any; Inner: typeof Inner; }
+>{} : { [x: string]: any; Inner: typeof Inner; }
 
 === tests/cases/conformance/salsa/a.js ===
 Outer.Inner = class {
 >Outer.Inner = class {    constructor() {        /** @type {number} */        this.y = 12    }} : typeof Inner
 >Outer.Inner : typeof Inner
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner: typeof Inner; }
 >Inner : typeof Inner
 >class {    constructor() {        /** @type {number} */        this.y = 12    }} : typeof Inner
 
@@ -35,7 +35,7 @@ var inner = new Outer.Inner()
 >inner : Inner
 >new Outer.Inner() : Inner
 >Outer.Inner : typeof Inner
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner: typeof Inner; }
 >Inner : typeof Inner
 
 inner.y
@@ -57,7 +57,7 @@ var z = new Outer.Inner()
 >z : Inner
 >new Outer.Inner() : Inner
 >Outer.Inner : typeof Inner
->Outer : typeof Outer
+>Outer : { [x: string]: any; Inner: typeof Inner; }
 >Inner : typeof Inner
 
 z.y
diff --git a/tests/cases/fourslash/jsSpecialAssignmentMerging.ts b/tests/cases/fourslash/jsSpecialAssignmentMerging.ts
new file mode 100644
index 0000000000000..fa093470baeaa
--- /dev/null
+++ b/tests/cases/fourslash/jsSpecialAssignmentMerging.ts
@@ -0,0 +1,22 @@
+/// <reference path="fourslash.ts" />
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: b.d.ts
+//// declare class C { }
+// @Filename: a.js
+//// C.prototype = { m: "q"; }
+// @Filename: test.js
+//// var c = new C()
+//// /*1*/
+//// var c = new C()
+
+// #24015
+// This failed with 13 and up on my machine, so 20 is 2**7 more than needed.
+for (let i = 0; i < 20; i++) {
+    goTo.marker('1');
+    edit.insertLine('c');
+
+    verify.getSemanticDiagnostics([])
+}