diff --git a/src/lib/es6.d.ts b/src/lib/es6.d.ts
index 8590e2273e0..83ae724b768 100644
--- a/src/lib/es6.d.ts
+++ b/src/lib/es6.d.ts
@@ -50,11 +50,6 @@ interface SymbolConstructor {
       */
     isConcatSpreadable: symbol;
 
-    /** 
-      * A Boolean value that if true indicates that an object may be used as a regular expression. 
-      */
-    isRegExp: symbol;
-
     /** 
       * A method that returns the default iterator for an object.Called by the semantics of the 
       * for-of statement. 
@@ -598,8 +593,6 @@ interface Math {
 }
 
 interface RegExp {
-    [Symbol.isRegExp]: boolean;
-
     /** 
       * Matches a string with a regular expression, and returns an array containing the results of 
       * that search.