diff --git a/dom/src/json/nsJSON.cpp b/dom/src/json/nsJSON.cpp
index 2dc1c36e16bf..88c5eec05aa7 100644
--- a/dom/src/json/nsJSON.cpp
+++ b/dom/src/json/nsJSON.cpp
@@ -634,8 +634,6 @@ nsJSONListener::OnDataAvailable(nsIRequest *aRequest, nsISupports *aContext,
                                 nsIInputStream *aStream,
                                 PRUint32 aOffset, PRUint32 aLength)
 {
-  PRUint32 contentLength;
-  aStream->Available(&contentLength);
   nsresult rv = NS_OK;
 
   if (mNeedsConverter && mSniffBuffer.Length() < 4) {