diff --git a/compiler/res/prog8lib/cx16/textio.p8 b/compiler/res/prog8lib/cx16/textio.p8
index 438f0e157..7a35eb6fa 100644
--- a/compiler/res/prog8lib/cx16/textio.p8
+++ b/compiler/res/prog8lib/cx16/textio.p8
@@ -169,13 +169,18 @@ sub color2 (ubyte txtcol, ubyte bgcol) {
 }
 
 sub lowercase() {
-    cx16.screen_set_charset(3, 0)  ; lowercase charset
+    cx16.screen_set_charset(3, 0)  ; lowercase petscii charset
 }
 
 sub uppercase() {
-    cx16.screen_set_charset(2, 0)  ; uppercase charset
+    cx16.screen_set_charset(2, 0)  ; uppercase petscii charset
 }
 
+sub iso() {
+    cx16.screen_set_charset(1, 0)  ; iso charset
+}
+
+
 asmsub  scroll_left() clobbers(A, Y)  {
 	; ---- scroll the whole screen 1 character to the left
 	;      contents of the rightmost column are unchanged, you should clear/refill this yourself