diff --git a/mozilla/content/base/src/nsXMLHttpRequest.cpp b/mozilla/content/base/src/nsXMLHttpRequest.cpp
index 19d0e0cd1fe..3eced146e9d 100644
--- a/mozilla/content/base/src/nsXMLHttpRequest.cpp
+++ b/mozilla/content/base/src/nsXMLHttpRequest.cpp
@@ -1998,7 +1998,7 @@ nsXMLHttpRequest::SetRequestHeader(const nsACString& header,
     const char *kInvalidHeaders[] = {
       "accept-charset", "accept-encoding", "connection", "content-length",
       "content-transfer-encoding", "date", "expect", "host", "keep-alive",
-      "referer", "access-control-origin", "te", "trailer",
+      "proxy-connection", "referer", "access-control-origin", "te", "trailer",
       "transfer-encoding", "upgrade", "via", "xmlhttprequest-security-check"
     };
     PRUint32 i;
@@ -2008,13 +2008,6 @@ nsXMLHttpRequest::SetRequestHeader(const nsACString& header,
         return NS_OK;
       }
     }
-    if (StringBeginsWith(header, NS_LITERAL_CSTRING("proxy-"),
-                         nsCaseInsensitiveCStringComparator()) ||
-        StringBeginsWith(header, NS_LITERAL_CSTRING("sec-"),
-                         nsCaseInsensitiveCStringComparator())) {
-      NS_WARNING("refusing to set request header");
-      return NS_OK;
-    }
   }
 
   // We need to set, not add to, the header.
diff --git a/mozilla/content/base/test/test_bug308484.html b/mozilla/content/base/test/test_bug308484.html
index 0941f594924..56a9c487e0e 100644
--- a/mozilla/content/base/test/test_bug308484.html
+++ b/mozilla/content/base/test/test_bug308484.html
@@ -20,27 +20,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=308484
 
 /** Test for Bug 308484 **/
 
-var headers = [
-  "aCCept-chaRset",
-  "acCePt-eNcoDing",
-  "coNnEctIon",
-  "coNtEnt-LEngth",
-  "cOntEnt-tRAnsFer-enCoDiNg",
-  "DATE",
-  "exPeCt",
-  "hOSt",
-  "keep-alive",
-  "reFERer",
-  "te",
-  "trAiLer",
-  "trANsfEr-eNcoDiNg",
-  "uPGraDe",
-  "viA",
-  "pRoxy-",
-  "sEc-",
-  "proxy-fOobar",
-  "sec-bAZbOx"
-];
+var headers = ["Host", "Content-Length", "Transfer-Encoding", "Via", "Upgrade"];
 var i, request;
 
 // Try setting headers in unprivileged context