diff --git a/transport.cpp b/transport.cpp
index 308ee8d..2bbbefd 100644
--- a/transport.cpp
+++ b/transport.cpp
@@ -603,15 +603,15 @@
 static void transport_unref(atransport* t) {
     CHECK(t != nullptr);
 
-    std::lock_guard<std::mutex> lock(transport_lock);
-    CHECK_GT(t->ref_count, 0u);
-    t->ref_count--;
-    if (t->ref_count == 0) {
+    size_t old_refcount = t->ref_count--;
+    CHECK_GT(old_refcount, 0u);
+
+    if (old_refcount == 1u) {
         D("transport: %s unref (kicking and closing)", t->serial);
         t->close(t);
         remove_transport(t);
     } else {
-        D("transport: %s unref (count=%zu)", t->serial, t->ref_count);
+        D("transport: %s unref (count=%zu)", t->serial, old_refcount - 1);
     }
 }
 
diff --git a/transport.h b/transport.h
index 57fc988..4a89ed9 100644
--- a/transport.h
+++ b/transport.h
@@ -61,7 +61,7 @@
     // class in one go is a very large change. Given how bad our testing is,
     // it's better to do this piece by piece.
 
-    atransport(ConnectionState state = kCsOffline) : connection_state_(state) {
+    atransport(ConnectionState state = kCsOffline) : ref_count(0), connection_state_(state) {
         transport_fde = {};
         protocol_version = A_VERSION;
         max_payload = MAX_PAYLOAD;
@@ -88,7 +88,7 @@
     int fd = -1;
     int transport_socket = -1;
     fdevent transport_fde;
-    size_t ref_count = 0;
+    std::atomic<size_t> ref_count;
     uint32_t sync_token = 0;
     bool online = false;
     TransportType type = kTransportAny;