diff --git a/src/FFmpeg.cpp b/src/FFmpeg.cpp
index f6851bd27..11cbec1b4 100644
--- a/src/FFmpeg.cpp
+++ b/src/FFmpeg.cpp
@@ -22,6 +22,7 @@ License: GPL v2.  See License.txt.
 #include "AudacityApp.h"
 #include "FileNames.h"
 #include "Internat.h"
+#include "widgets/HelpSystem.h"
 
 #include <wx/file.h>