diff --git a/src/posix/unix/gtk_dialogs.cpp b/src/posix/unix/gtk_dialogs.cpp
index b5fbfdd38..6a3042e44 100644
--- a/src/posix/unix/gtk_dialogs.cpp
+++ b/src/posix/unix/gtk_dialogs.cpp
@@ -61,6 +61,7 @@ typedef enum
 #include "startupinfo.h"
 #include "cmdlib.h"
 #include "i_interface.h"
+#include "printf.h"
 
 EXTERN_CVAR (Bool, queryiwad);