diff --git a/asminc/cbm510.inc b/asminc/cbm510.inc
index e98ed4a14..c4476c2e1 100644
--- a/asminc/cbm510.inc
+++ b/asminc/cbm510.inc
@@ -11,7 +11,6 @@
 
 ExecReg		= $00
 IndReg		= $01
-DEVNUM		= $9F
 
 ; ---------------------------------------------------------------------------
 ; Screen size
diff --git a/asminc/cbm610.inc b/asminc/cbm610.inc
index 62d0c6a42..14bbb3d69 100644
--- a/asminc/cbm610.inc
+++ b/asminc/cbm610.inc
@@ -11,7 +11,6 @@
 
 ExecReg		= $00
 IndReg		= $01
-DEVNUM		= $9F
 
 ; ---------------------------------------------------------------------------
 ; Screen size
diff --git a/libsrc/cbm510/crt0.s b/libsrc/cbm510/crt0.s
index fc8acee74..e89bae74f 100644
--- a/libsrc/cbm510/crt0.s
+++ b/libsrc/cbm510/crt0.s
@@ -64,6 +64,7 @@
 
 .proc   transfer_table
 
+        .byte   $9F, DEVNUM
         .byte   $CA, CURS_Y
         .byte   $CB, CURS_X
         .byte   $EC, CHARCOLOR
diff --git a/libsrc/cbm510/devnum.s b/libsrc/cbm510/devnum.s
index 0c6bf2130..a10004e85 100644
--- a/libsrc/cbm510/devnum.s
+++ b/libsrc/cbm510/devnum.s
@@ -2,6 +2,6 @@
 ; Oliver Schmidt, 2010-02-14
 ;
 
-	.include	"cbm510.inc"
+	.include	"extzp.inc"
 
 	.exportzp	devnum := DEVNUM
diff --git a/libsrc/cbm510/extzp.inc b/libsrc/cbm510/extzp.inc
index be0cba71f..f500c9bca 100644
--- a/libsrc/cbm510/extzp.inc
+++ b/libsrc/cbm510/extzp.inc
@@ -11,7 +11,7 @@
 
         .globalzp       sysp0, time, segsave, ktmp, CURS_X, CURS_Y, CURS_FLAG
         .globalzp       CURS_STATE, CURS_BLINK, CURS_COLOR, CHARCOLOR, RVS
-        .globalzp       SCREEN_PTR, CRAM_PTR
+        .globalzp       DEVNUM, SCREEN_PTR, CRAM_PTR
         .globalzp       keyidx, keybuf, keyscanbuf, keysave, modkey
         .globalzp       norkey, graphmode, lastidx, rptdelay, rptcount
 
diff --git a/libsrc/cbm510/extzp.s b/libsrc/cbm510/extzp.s
index 8402a00a8..abbfd2c43 100644
--- a/libsrc/cbm510/extzp.s
+++ b/libsrc/cbm510/extzp.s
@@ -43,6 +43,7 @@ CURS_BLINK:     .byte   0
 CURS_COLOR:     .byte   0
 CHARCOLOR:      .byte   0
 RVS:            .byte   0
+DEVNUM:         .byte   0
 SCREEN_PTR:     .word   0
 CRAM_PTR:       .word   0
 ; Stuff for our own kbd polling routine
diff --git a/libsrc/cbm610/crt0.s b/libsrc/cbm610/crt0.s
index c63bdfdb5..21874438a 100644
--- a/libsrc/cbm610/crt0.s
+++ b/libsrc/cbm610/crt0.s
@@ -63,6 +63,7 @@
 
 .proc   transfer_table
 
+        .byte   $9F, DEVNUM
         .byte   $CA, CURS_Y
         .byte   $CB, CURS_X
         .byte   $CC, graphmode
diff --git a/libsrc/cbm610/devnum.s b/libsrc/cbm610/devnum.s
index 75fa4cd2a..a10004e85 100644
--- a/libsrc/cbm610/devnum.s
+++ b/libsrc/cbm610/devnum.s
@@ -2,6 +2,6 @@
 ; Oliver Schmidt, 2010-02-14
 ;
 
-	.include	"cbm610.inc"
+	.include	"extzp.inc"
 
 	.exportzp	devnum := DEVNUM
diff --git a/libsrc/cbm610/extzp.inc b/libsrc/cbm610/extzp.inc
index bb46a185b..59eb824eb 100644
--- a/libsrc/cbm610/extzp.inc
+++ b/libsrc/cbm610/extzp.inc
@@ -9,8 +9,8 @@
         .globalzp       sysp1, sysp3, crtc, sid, ipccia, cia, acia, tpi1, tpi2
         .globalzp       ktab1, ktab2, ktab3, ktab4
 
-        .globalzp       sysp0, time, segsave, ktmp, CURS_X, CURS_Y, RVS, config
-        .globalzp       CharPtr, keyidx, keybuf, keyscanbuf, keysave
+        .globalzp       sysp0, time, segsave, ktmp, CURS_X, CURS_Y, RVS, DEVNUM
+        .globalzp       config, CharPtr, keyidx, keybuf, keyscanbuf, keysave
         .globalzp       modkey, norkey, graphmode, lastidx, rptdelay, rptcount
 
 
diff --git a/libsrc/cbm610/extzp.s b/libsrc/cbm610/extzp.s
index be7e096df..b0f3e7688 100644
--- a/libsrc/cbm610/extzp.s
+++ b/libsrc/cbm610/extzp.s
@@ -37,6 +37,7 @@ ktmp:           .byte   0
 CURS_X:         .byte   0
 CURS_Y:         .byte   0
 RVS:            .byte   0
+DEVNUM:         .byte   0
 config:         .byte   0
 CharPtr:        .word   0
 ; Stuff for our own kbd polling routine