diff --git a/mozilla/docshell/base/nsIDocShell.idl b/mozilla/docshell/base/nsIDocShell.idl
index ec691ff06ac..2c6b26928e6 100644
--- a/mozilla/docshell/base/nsIDocShell.idl
+++ b/mozilla/docshell/base/nsIDocShell.idl
@@ -71,7 +71,8 @@ interface nsIDocShell : nsISupports
 	@param aStream - The input stream that provides access to the data to be loaded.
 	@param aURI	   - The URI representing the stream, or null.
 	@param aContentType - The type (MIME) of data being loaded.
-	@param aContentLen  - The length (in bytes) of the stream.
+	@param aContentLen  - The length (in bytes) of the stream.  If you don't know
+        the length of the stream this can be -1.
 	@param aLoadInfo - This is the extended load info for this load.  This most
 		most often will be null, but if you need to do additional setup for this
 		load you can get a loadInfo object by calling createLoadInfo.  Once you have