diff --git a/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp b/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
index dd801120857b..56ee35a66d00 100644
--- a/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
+++ b/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
@@ -1542,15 +1542,15 @@ void nsHttpChannelAuthProvider::SetAuthorizationHeader(
   // or a webserver
   nsISupports **continuationState;
 
+  nsAutoCString suffix;
   if (header == nsHttp::Proxy_Authorization) {
     continuationState = &mProxyAuthContinuationState;
   } else {
     continuationState = &mAuthContinuationState;
-  }
 
-  nsCOMPtr<nsIChannel> chan = do_QueryInterface(mAuthChannel);
-  nsAutoCString suffix;
-  GetOriginAttributesSuffix(chan, suffix);
+    nsCOMPtr<nsIChannel> chan = do_QueryInterface(mAuthChannel);
+    GetOriginAttributesSuffix(chan, suffix);
+  }
 
   rv = authCache->GetAuthEntryForPath(scheme, host, port, path, suffix, &entry);
   if (NS_SUCCEEDED(rv)) {
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_auth.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_auth.js
index 37e9c3962e80..56fbffb66a41 100644
--- a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_auth.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_auth.js
@@ -1,5 +1,9 @@
 "use strict";
 
+XPCOMUtils.defineLazyServiceGetter(this, "authManager",
+                                   "@mozilla.org/network/http-auth-manager;1",
+                                   "nsIHttpAuthManager");
+
 const proxy = createHttpServer();
 
 // accept proxy connections for mozilla.org
@@ -74,6 +78,8 @@ add_task(async function test_webRequest_auth_proxy() {
   await handlingExt.startup();
   await handlingExt.awaitMessage("pac-ready");
 
+  authManager.clearAll();
+
   let contentPage = await ExtensionTestUtils.loadContentPage(`http://mozilla.org/`);
 
   await handlingExt.awaitMessage("done");
@@ -112,12 +118,12 @@ add_task(async function test_webRequest_auth_proxy_system() {
       xhr.open("GET", url);
       xhr.onload = () => { resolve(xhr.responseText); };
       xhr.onerror = () => { reject(xhr.status); };
-      // use a different contextId to avoid auth cache.
-      xhr.setOriginAttributes({userContextId: 1});
       xhr.send();
     });
   }
 
+  authManager.clearAll();
+
   await Promise.all([
     handlingExt.awaitMessage("onAuthRequired"),
     fetch("http://mozilla.org"),
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js
index 4a5f37d59f96..73fac0d89e92 100644
--- a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js
@@ -1,5 +1,9 @@
 "use strict";
 
+XPCOMUtils.defineLazyServiceGetter(this, "authManager",
+                                   "@mozilla.org/network/http-auth-manager;1",
+                                   "nsIHttpAuthManager");
+
 const proxy = createHttpServer();
 
 // accept proxy connections for mozilla.org
@@ -76,6 +80,8 @@ add_task(async function test_webRequest_auth_proxy() {
   await handlingExt.startup();
   await handlingExt.awaitMessage("ready");
 
+  authManager.clearAll();
+
   let contentPage = await ExtensionTestUtils.loadContentPage(`http://mozilla.org/`);
 
   await handlingExt.awaitMessage("done");
@@ -112,6 +118,8 @@ add_task(async function test_webRequest_auth_proxy_system() {
   await handlingExt.startup();
   await handlingExt.awaitMessage("ready");
 
+  authManager.clearAll();
+
   function fetch(url) {
     return new Promise((resolve, reject) => {
       let xhr = new XMLHttpRequest();
@@ -119,8 +127,6 @@ add_task(async function test_webRequest_auth_proxy_system() {
       xhr.open("GET", url);
       xhr.onload = () => { resolve(xhr.responseText); };
       xhr.onerror = () => { reject(xhr.status); };
-      // use a different contextId to avoid auth cache.
-      xhr.setOriginAttributes({userContextId: 1});
       xhr.send();
     });
   }