diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index e717efa5dba70..4e84cf197ad19 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2336,7 +2336,7 @@ namespace ts {
                     // For `f.prototype.m = function() { this.x = 0; }`, `this.x = 0` should modify `f`'s members, not the function expression.
                     if (isBinaryExpression(thisContainer.parent) && thisContainer.parent.operatorToken.kind === SyntaxKind.EqualsToken) {
                         const l = thisContainer.parent.left;
-                        if (isPropertyAccessExpression(l) && isPropertyAccessExpression(l.expression) && l.expression.name.escapedText === "prototype" && isEntityNameExpression(l.expression.expression)) {
+                        if (isPropertyAccessEntityNameExpression(l) && isPrototypeAccess(l.expression)) {
                             constructorSymbol = getJSInitializerSymbolFromName(l.expression.expression, containerContainer);
                         }
                     }
@@ -2368,12 +2368,12 @@ namespace ts {
             if (node.expression.kind === SyntaxKind.ThisKeyword) {
                 bindThisPropertyAssignment(node);
             }
-            else if (isEntityNameExpression(node) && node.parent.parent.kind === SyntaxKind.SourceFile) {
-                if (isPropertyAccessExpression(node.expression) && node.expression.name.escapedText === "prototype") {
-                    bindPrototypePropertyAssignment(node as PropertyAccessEntityNameExpression, node.parent);
+            else if (isPropertyAccessEntityNameExpression(node) && node.parent.parent.kind === SyntaxKind.SourceFile) {
+                if (isPrototypeAccess(node.expression)) {
+                    bindPrototypePropertyAssignment(node, node.parent);
                 }
                 else {
-                    bindStaticPropertyAssignment(node as PropertyAccessEntityNameExpression);
+                    bindStaticPropertyAssignment(node);
                 }
             }
         }
@@ -2436,15 +2436,10 @@ namespace ts {
 
         function bindPropertyAssignment(name: EntityNameExpression, propertyAccess: PropertyAccessEntityNameExpression, isPrototypeProperty: boolean) {
             let symbol = getJSInitializerSymbolFromName(name);
-            let isToplevelNamespaceableInitializer: boolean;
-            if (isBinaryExpression(propertyAccess.parent)) {
-                const isPrototypeAssignment = isPropertyAccessExpression(propertyAccess.parent.left) && propertyAccess.parent.left.name.escapedText === "prototype";
-                isToplevelNamespaceableInitializer = propertyAccess.parent.parent.parent.kind === SyntaxKind.SourceFile &&
-                    !!getJavascriptInitializer(propertyAccess.parent.right, isPrototypeAssignment);
-            }
-            else {
-                isToplevelNamespaceableInitializer = propertyAccess.parent.parent.kind === SyntaxKind.SourceFile;
-            }
+            const isToplevelNamespaceableInitializer = isBinaryExpression(propertyAccess.parent)
+                ? propertyAccess.parent.parent.parent.kind === SyntaxKind.SourceFile &&
+                    !!getJavascriptInitializer(propertyAccess.parent.right, isPrototypeAccess(propertyAccess.parent.left))
+                : propertyAccess.parent.parent.kind === SyntaxKind.SourceFile;
             if (!isPrototypeProperty && (!symbol || !(symbol.flags & SymbolFlags.Namespace)) && isToplevelNamespaceableInitializer) {
                 // make symbols or add declarations for intermediate containers
                 const flags = SymbolFlags.Module | SymbolFlags.JSContainer;
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2dcea191b5493..629ce86c9b67e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18069,8 +18069,7 @@ namespace ts {
                 parent = parent.parent;
             }
             return parent && isBinaryExpression(parent) &&
-                isPropertyAccessExpression(parent.left) &&
-                parent.left.name.escapedText === "prototype" &&
+                isPrototypeAccess(parent.left) &&
                 parent.operatorToken.kind === SyntaxKind.EqualsToken &&
                 isObjectLiteralExpression(parent.right) &&
                 parent.right;
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 4077d33933e11..60b140adacecb 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1509,7 +1509,7 @@ namespace ts {
      */
     export function getAssignedJavascriptInitializer(node: Node) {
         if (node && node.parent && isBinaryExpression(node.parent) && node.parent.operatorToken.kind === SyntaxKind.EqualsToken) {
-            const isPrototypeAssignment = isPropertyAccessExpression(node.parent.left) && node.parent.left.name.escapedText === "prototype";
+            const isPrototypeAssignment = isPrototypeAccess(node.parent.left);
             return getJavascriptInitializer(node.parent.right, isPrototypeAssignment) ||
                 getDefaultedJavascriptInitializer(node.parent.left as EntityNameExpression, node.parent.right, isPrototypeAssignment);
         }
@@ -1629,7 +1629,7 @@ namespace ts {
                 // F.prototype = { ... }
                 return SpecialPropertyAssignmentKind.Prototype;
             }
-            else if (isPropertyAccessExpression(lhs.expression) && lhs.expression.name.escapedText === "prototype") {
+            else if (isPrototypeAccess(lhs.expression)) {
                 // F.G....prototype.x = expr
                 return SpecialPropertyAssignmentKind.PrototypeProperty;
             }
@@ -3336,8 +3336,15 @@ namespace ts {
     }
 
     export function isEntityNameExpression(node: Node): node is EntityNameExpression {
-        return node.kind === SyntaxKind.Identifier ||
-            node.kind === SyntaxKind.PropertyAccessExpression && isEntityNameExpression((<PropertyAccessExpression>node).expression);
+        return node.kind === SyntaxKind.Identifier || isPropertyAccessEntityNameExpression(node);
+    }
+
+    export function isPropertyAccessEntityNameExpression(node: Node): node is PropertyAccessEntityNameExpression {
+        return isPropertyAccessExpression(node) && isEntityNameExpression(node.expression);
+    }
+
+    export function isPrototypeAccess(node: Node): node is PropertyAccessExpression {
+        return isPropertyAccessExpression(node) && node.name.escapedText === "prototype";
     }
 
     export function isRightSideOfQualifiedNameOrPropertyAccess(node: Node) {