diff --git a/netwerk/protocol/http/nsHttpConnectionMgr.cpp b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
index 5c40ca543dcc..f9dcabb63c04 100644
--- a/netwerk/protocol/http/nsHttpConnectionMgr.cpp
+++ b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
@@ -446,6 +446,7 @@ nsHttpConnectionMgr::LookupConnectionEntry(nsHttpConnectionInfo *ci,
                                            nsHttpConnection *conn,
                                            nsHttpTransaction *trans)
 {
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
     if (!ci)
         return nullptr;
 
@@ -574,6 +575,8 @@ void
 nsHttpConnectionMgr::ReportSpdyCWNDSetting(nsHttpConnectionInfo *ci,
                                            uint32_t cwndValue)
 {
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
+
     if (!gHttpHandler->UseSpdyPersistentSettings())
         return;
 
@@ -600,6 +603,8 @@ nsHttpConnectionMgr::ReportSpdyCWNDSetting(nsHttpConnectionInfo *ci,
 uint32_t
 nsHttpConnectionMgr::GetSpdyCWNDSetting(nsHttpConnectionInfo *ci)
 {
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
+
     if (!gHttpHandler->UseSpdyPersistentSettings())
         return 0;
 
@@ -886,6 +891,7 @@ nsHttpConnectionMgr::PruneDeadConnectionsCB(const nsACString &key,
                                             nsAutoPtr<nsConnectionEntry> &ent,
                                             void *closure)
 {
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
     nsHttpConnectionMgr *self = (nsHttpConnectionMgr *) closure;
 
     LOG(("  pruning [ci=%s]\n", ent->mConnInfo->HashKey().get()));
@@ -2222,6 +2228,7 @@ void
 nsHttpConnectionMgr::OnMsgClosePersistentConnections(int32_t, void *)
 {
     LOG(("nsHttpConnectionMgr::OnMsgClosePersistentConnections\n"));
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
 
     mCT.Enumerate(ClosePersistentConnectionsCB, this);
 }
@@ -3387,6 +3394,7 @@ nsHttpConnectionMgr::GetConnectionData(nsTArray<mozilla::net::HttpRetParams> *aA
 void
 nsHttpConnectionMgr::ResetIPFamillyPreference(nsHttpConnectionInfo *ci)
 {
+    MOZ_ASSERT(PR_GetCurrentThread() == gSocketThread);
     nsConnectionEntry *ent = LookupConnectionEntry(ci, nullptr, nullptr);
     if (ent)
         ent->ResetIPFamilyPreference();
diff --git a/netwerk/test/unit/test_freshconnection.js b/netwerk/test/unit/test_freshconnection.js
new file mode 100644
index 000000000000..cf92c4d40a56
--- /dev/null
+++ b/netwerk/test/unit/test_freshconnection.js
@@ -0,0 +1,31 @@
+// This is essentially a debug mode crashtest to make sure everything
+// involved in a reload runs on the right thread. It relies on the
+// assertions in necko.
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+var listener = {
+  onStartRequest: function test_onStartR(request, ctx) {
+  },
+
+  onDataAvailable: function test_ODA() {
+    do_throw("Should not get any data!");
+  },
+
+  onStopRequest: function test_onStopR(request, ctx, status) {
+    do_test_finished();
+  },
+};
+
+function run_test() {
+  var ios = Cc["@mozilla.org/network/io-service;1"].
+                       getService(Ci.nsIIOService);
+  var chan = ios.newChannel("http://localhost:4444", "", null);
+  chan.loadFlags = Ci.nsIRequest.LOAD_FRESH_CONNECTION |
+	           Ci.nsIChannel.LOAD_INITIAL_DOCUMENT_URI;
+  chan.QueryInterface(Ci.nsIHttpChannel);
+  chan.asyncOpen(listener, null);
+  do_test_pending();
+}
+
diff --git a/netwerk/test/unit/xpcshell.ini b/netwerk/test/unit/xpcshell.ini
index 41f97ba2279c..63dcfbc594d8 100644
--- a/netwerk/test/unit/xpcshell.ini
+++ b/netwerk/test/unit/xpcshell.ini
@@ -107,6 +107,7 @@ tail =
 [test_file_partial_inputstream.js]
 [test_file_protocol.js]
 [test_filestreams.js]
+[test_freshconnection.js]
 [test_gre_resources.js]
 [test_gzipped_206.js]
 [test_head.js]