diff --git a/polio.s b/polio.s
index 5db7ffb..49ea080 100644
--- a/polio.s
+++ b/polio.s
@@ -40,8 +40,13 @@ dosdbt:                    # assumes es=0
 
     .section .text.int80stuff
 
-# near copy [param 2] bytes, es:[param 0] -> es:[param 1]
+# near copy [param 2] bytes, ds:[param 0] -> ds:[param 1]
 copy:
+    mov ax, [bp-14]     # ds
+    mov es, ax
+    mov ds, ax
+    mov cl, 4
+    shl si, cl
     mov si, [bp+0]      # source
     mov di, [bp+2]      # destination
     mov cx, [bp+4]      # length
@@ -107,20 +112,36 @@ formattrack:
     int 0x13
     ret
 
+# params: ds:fname, ds:dest
 readfile:
+    mov si, [bp-14] # ds
+    mov cl, 4
+    shl si, cl
     mov ax, [bp+0]
+    add ax, si
     mov dx, [bp+2]
+    add dx, si
     call fat12_readfile
     ret
 
+# params: ds:addr, size
 sendpara:
+    mov si, [bp-14] # ds
+    mov cl, 4
+    shl si, cl
     mov ax, [bp+0]
+    add ax, si
     mov dx, [bp+2]
     call parasend
     ret
 
+# params: ds:addr, size
 recvpara:
+    mov si, [bp-14] # ds
+    mov cl, 4
+    shl si, cl
     mov ax, [bp+0]
+    add ax, si
     mov dx, [bp+2]
     call pararecv
     ret
@@ -144,7 +165,7 @@ int80h:
     mov si, ax
     mov bp, sp
     lea bp, [bp + 16]       # 10 for us, 6 for the interrupt
-    call [int80h_table+si]
+    call cs:[int80h_table+si]
     jmp 1f
 0:
     mov ax, -1