diff --git a/src/event/Loop.cxx b/src/event/Loop.cxx
index 376e10300..6d78070a1 100644
--- a/src/event/Loop.cxx
+++ b/src/event/Loop.cxx
@@ -21,9 +21,12 @@
 #include "TimerEvent.hxx"
 #include "SocketMonitor.hxx"
 #include "IdleEvent.hxx"
-#include "DeferEvent.hxx"
 #include "util/ScopeExit.hxx"
 
+#ifdef HAVE_THREADED_EVENT_LOOP
+#include "DeferEvent.hxx"
+#endif
+
 #ifdef HAVE_URING
 #include "UringManager.hxx"
 #include "util/PrintException.hxx"