diff --git a/c64/kernal/ioinit.s b/c64/kernal/ioinit.s
index bbde4691..fd25f891 100644
--- a/c64/kernal/ioinit.s
+++ b/c64/kernal/ioinit.s
@@ -1,3 +1,12 @@
 ; Function defined on pp272-273 of C64 Programmers Reference Guide
 ioinit:
+
+	; Set $00/$01 port mode and value
+	; We want BASIC and KERNAL ROMs mapped, and datasette motor off
+	; (https://www.c64-wiki.com/wiki/Zeropage)
+	LDA #$2F
+	STA $00
+	LDA #$27
+	STA $01
+
 	rts