diff --git a/libtransmission/session-thread.cc b/libtransmission/session-thread.cc
index 53cd0fb5e..b6db637d9 100644
--- a/libtransmission/session-thread.cc
+++ b/libtransmission/session-thread.cc
@@ -107,7 +107,8 @@ int cond_wait(void* vcond, void* vlock, struct timeval const* tv)
 
 unsigned long thread_current_id()
 {
-    return std::hash<std::thread::id>()(std::this_thread::get_id());
+    thread_local auto const hashed = std::hash<std::thread::id>()(std::this_thread::get_id());
+    return hashed;
 }
 
 void initEvthreadsOnce()