diff --git a/src/x86_stage1.S b/src/x86_stage1.S
index aa8f585..cbcfb3f 100644
--- a/src/x86_stage1.S
+++ b/src/x86_stage1.S
@@ -7,6 +7,9 @@
 _start:
     ljmp $0, $(start - _start + 0x7c00)
 
+disk:
+    .byte 0
+
 start:
     cli
     xor %ax, %ax
@@ -17,6 +20,8 @@ start:
     mov %ax, %gs
     mov $0x2000, %sp
 
+    mov %dl, (disk - _start + 0x7c00)
+
     mov $0x02,   %ah
     mov $1,      %al /* Sectors count       */
     mov $0x80,   %dl /* Drive               */