diff --git a/mozilla/js/src/jsscan.c b/mozilla/js/src/jsscan.c
index 4f55233f519..e4994eb4a49 100644
--- a/mozilla/js/src/jsscan.c
+++ b/mozilla/js/src/jsscan.c
@@ -1,5 +1,5 @@
 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
- * vim: set sw=4 ts=8 et tw=80:
+ * vim: set sw=4 ts=8 et tw=78:
  *
  * ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
@@ -477,6 +477,11 @@ PeekChar(JSTokenStream *ts)
     return c;
 }
 
+/*
+ * Peek n chars ahead into ts.  Return true if n chars were read, false if
+ * there weren't enough characters in the input stream.  This function cannot
+ * be used to peek into or past a newline.
+ */
 static JSBool
 PeekChars(JSTokenStream *ts, intN n, jschar *cp)
 {
@@ -487,6 +492,10 @@ PeekChars(JSTokenStream *ts, intN n, jschar *cp)
         c = GetChar(ts);
         if (c == EOF)
             break;
+        if (c == '\n') {
+            UngetChar(ts, c);
+            break;
+        }
         cp[i] = (jschar)c;
     }
     for (j = i - 1; j >= 0; j--)