diff --git a/include/wx/gtk/window.h b/include/wx/gtk/window.h
index fa3ae5c104..171f34fac9 100644
--- a/include/wx/gtk/window.h
+++ b/include/wx/gtk/window.h
@@ -20,10 +20,6 @@
     #define WXUNUSED_IN_GTK3(x) x
 #endif
 
-// helper structure that holds class that holds GtkIMContext object and
-// some additional data needed for key events processing
-struct wxGtkIMData;
-
 typedef struct _GdkEventKey GdkEventKey;
 typedef struct _GtkIMContext GtkIMContext;
 
diff --git a/include/wx/gtk1/window.h b/include/wx/gtk1/window.h
index 388f06fd91..43d8be0524 100644
--- a/include/wx/gtk1/window.h
+++ b/include/wx/gtk1/window.h
@@ -16,10 +16,6 @@ typedef struct _GdkIC GdkIC;
 typedef struct _GdkICAttr GdkICAttr;
 #endif
 
-// helper structure that holds class that holds GtkIMContext object and
-// some additional data needed for key events processing
-struct wxGtkIMData;
-
 //-----------------------------------------------------------------------------
 // callback definition for inserting a window (internal)
 //-----------------------------------------------------------------------------