diff --git a/src/unix/utilsx11.cpp b/src/unix/utilsx11.cpp
index 04f061bb20..b9b5a4d40e 100644
--- a/src/unix/utilsx11.cpp
+++ b/src/unix/utilsx11.cpp
@@ -24,6 +24,7 @@
 #endif
 
 #include "wx/iconbndl.h"
+#include "wx/apptrait.h"
 
 #ifdef __VMS
 #pragma message disable nosimpint