diff --git a/src/GUI/LocalAircraftCache.cxx b/src/GUI/LocalAircraftCache.cxx
index 2a01f7f70..9dc929296 100644
--- a/src/GUI/LocalAircraftCache.cxx
+++ b/src/GUI/LocalAircraftCache.cxx
@@ -20,6 +20,8 @@
 
 #include "LocalAircraftCache.hxx"
 
+#include <cassert>
+
 #include <QDir>
 #include <QThread>
 #include <QMutex>