diff --git a/srtcore/core.cpp b/srtcore/core.cpp
index b7f2723c2..83ff52f16 100644
--- a/srtcore/core.cpp
+++ b/srtcore/core.cpp
@@ -9992,12 +9992,13 @@ bool srt::CUDT::overrideSndSeqNo(int32_t seq)
 int srt::CUDT::checkLazySpawnTsbPdThread()
 {
     const bool need_tsbpd = m_bTsbPd || m_bGroupTsbPd;
+    if (!need_tsbpd)
+        return 0;
 
-    if (need_tsbpd && !m_RcvTsbPdThread.joinable())
+    ScopedLock lock(m_RcvTsbPdStartupLock);
+    if (!m_RcvTsbPdThread.joinable())
     {
-        ScopedLock lock(m_RcvTsbPdStartupLock);
-
-        if (m_bClosing) // Check again to protect join() in CUDT::releaseSync()
+        if (m_bClosing) // Check m_bClosing to protect join() in CUDT::releaseSync().
             return -1;
 
         HLOGP(qrlog.Debug, "Spawning Socket TSBPD thread");
diff --git a/srtcore/core.h b/srtcore/core.h
index e24bd8152..3935b99d3 100644
--- a/srtcore/core.h
+++ b/srtcore/core.h
@@ -995,7 +995,7 @@ class CUDT
     sync::CThread m_RcvTsbPdThread;              // Rcv TsbPD Thread handle
     sync::Condition m_RcvTsbPdCond;              // TSBPD signals if reading is ready. Use together with m_RecvLock
     bool m_bTsbPdNeedsWakeup;                    // Signal TsbPd thread to wake up on RCV buffer state change.
-    sync::Mutex m_RcvTsbPdStartupLock;           // Protects TSBPD thread creating and joining
+    sync::Mutex m_RcvTsbPdStartupLock;           // Protects TSBPD thread creation and joining.
 
     CallbackHolder<srt_listen_callback_fn> m_cbAcceptHook;
     CallbackHolder<srt_connect_callback_fn> m_cbConnectHook;