diff --git a/lcl/interfaces/gtk/gtkproc.inc b/lcl/interfaces/gtk/gtkproc.inc
index ff6ed3867e..30ffce8167 100644
--- a/lcl/interfaces/gtk/gtkproc.inc
+++ b/lcl/interfaces/gtk/gtkproc.inc
@@ -2067,7 +2067,7 @@ var
   begin
     Length := 1;
     {$ifndef gtk1}
-    if C in [#$1..#$20] then
+    if C in [#$01..#$1B] then
     begin
       KeyVal := $FF00 or Ord(C);
       if KeyVal = GDK_KEY_BackSpace then