diff --git a/src/unix/displayx11.cpp b/src/unix/displayx11.cpp
index 687329efd2..87ab205039 100644
--- a/src/unix/displayx11.cpp
+++ b/src/unix/displayx11.cpp
@@ -343,6 +343,7 @@ void wxClientDisplayRect(int *x, int *y, int *width, int *height)
 
 #else // !wxUSE_LIBHILDON
 
+#include <X11/Xlib.h>
 #include <X11/Xatom.h>
 
 // TODO: make this a full-fledged class and move to a public header