diff --git a/user/src/com/google/gwt/resources/css/GenerateCssAst.java b/user/src/com/google/gwt/resources/css/GenerateCssAst.java
index 2b264d3..4175fcc 100644
--- a/user/src/com/google/gwt/resources/css/GenerateCssAst.java
+++ b/user/src/com/google/gwt/resources/css/GenerateCssAst.java
@@ -478,9 +478,9 @@
     }
 
     void parseExternal(String atRule) throws CSSException {
-      // @external .foo, bar; Drop the dots and commas
-      String[] parts = atRule.substring(10, atRule.length() - 1).replaceAll(
-          "(, *)|( +)", " ").replaceAll("\\.", "").split(" ");
+      // @external .foo, bar; Drop the dots, commas and ignore whitespace
+      String[] parts = atRule.substring("@external ".length(), atRule.length() - 1).replaceAll(
+          "(,|\\s)\\s*", " ").replaceAll("\\.", "").split(" ");
 
       CssExternalSelectors externals = new CssExternalSelectors();
       Collections.addAll(externals.getClasses(), parts);