diff --git a/src/services/services.ts b/src/services/services.ts
index 56e68b2f5a1..ad6643faf3c 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -5520,7 +5520,7 @@ module ts {
                         var defaultLibFile = getDefaultLibFileName(host.getCompilationSettings());
                         for (var i = 0; i < declarations.length; i++) {
                             var sourceFile = declarations[i].getSourceFile();
-                            if (sourceFile && endsWith(sourceFile.fileName, defaultLibFile)) {
+                            if (sourceFile && isDefaultLibFile(sourceFile.fileName, defaultLibFile)) {
                                 return getRenameInfoError(getLocaleSpecificMessage(Diagnostics.You_cannot_rename_elements_that_are_defined_in_the_standard_TypeScript_library.key));
                             }
                         }
@@ -5543,8 +5543,14 @@ module ts {
 
             return getRenameInfoError(getLocaleSpecificMessage(Diagnostics.You_cannot_rename_this_element.key));
 
-            function endsWith(string: string, value: string): boolean {
-                return string.lastIndexOf(value) + value.length === string.length;
+            function isDefaultLibFile(fileName: string, defaultLibFile: string): boolean {
+                var hasValidPrefix = true;
+                var index = fileName.lastIndexOf(defaultLibFile);
+                if (index - 1 >= 0) {
+                    var prefix = fileName[index - 1];
+                    hasValidPrefix = (prefix === "\\" || prefix === "/");
+                }
+                return index >= 0 && hasValidPrefix && (index + defaultLibFile.length === fileName.length);
             }
 
             function getRenameInfoError(localizedErrorMessage: string): RenameInfo {