diff --git a/libsrc/cbm/oserrlist.s b/libsrc/cbm/oserrlist.s
index 2f980971e..a8e64c7cb 100644
--- a/libsrc/cbm/oserrlist.s
+++ b/libsrc/cbm/oserrlist.s
@@ -1,6 +1,6 @@
 ;
 ; 2002-07-18, Ullrich von Bassewitz
-; 2014-05-26, Greg King
+; 2014-05-28, Greg King
 ;
 ; Defines the platform-specific error list.
 ;
@@ -50,22 +50,23 @@ __sys_oserrlist:
         sys_oserr_entry          7, "File not output"
         sys_oserr_entry          8, "Filename missing"
         sys_oserr_entry          9, "Illegal device"
-        sys_oserr_entry         20, "No sector header"
-        sys_oserr_entry         21, "No sync mark"
-        sys_oserr_entry         22, "No sector data"
-        sys_oserr_entry         23, "Checksum error"
-        sys_oserr_entry         24, "Decode error"
-        sys_oserr_entry         25, "Verify error"
-        sys_oserr_entry         26, "Write protect on"
-        sys_oserr_entry         27, "Checksum error"
-        sys_oserr_entry         28, "Write overrun"
+        sys_oserr_entry         20, "Read error (No sector header)"
+        sys_oserr_entry         21, "Read error (No sync mark)"
+        sys_oserr_entry         22, "Read error (No sector data)"
+        sys_oserr_entry         23, "Read error (Bad data checksum)"
+        sys_oserr_entry         24, "Read error (Decoding problem)"
+        sys_oserr_entry         25, "Write error (Verify failed)"
+        sys_oserr_entry         26, "Write protected"
+        sys_oserr_entry         27, "Read error (Bad header checksum)"
+        sys_oserr_entry         28, "Write error (overrun)"
         sys_oserr_entry         29, "Disk ID mismatch"
-        sys_oserr_entry         30, "Command not recognized"
-        sys_oserr_entry         31, "Command not implemented"
-        sys_oserr_entry         32, "Command too long"
-        sys_oserr_entry         33, "Invalid write filename"
-        sys_oserr_entry         34, "No file given"
-        sys_oserr_entry         39, "File not found"
+        sys_oserr_entry         30, "Syntax error (Command not recognized)"
+        sys_oserr_entry         31, "Syntax error (Command not implemented)"
+        sys_oserr_entry         32, "Syntax error (Command too long)"
+        sys_oserr_entry         33, "Syntax error (Invalid write filename)"
+        sys_oserr_entry         34, "Syntax error (No file given)"
+        sys_oserr_entry         39, "System file not found"
+        sys_oserr_entry         49, "Invalid format"
         sys_oserr_entry         50, "Record not present"
         sys_oserr_entry         51, "Overflow in record"
         sys_oserr_entry         52, "File too large"
@@ -82,4 +83,7 @@ __sys_oserrlist:
         sys_oserr_entry         72, "Disk full"
         sys_oserr_entry         73, "DOS version mismatch"
         sys_oserr_entry         74, "Drive not ready"
+        sys_oserr_entry         75, "Format error"
+        sys_oserr_entry         77, "Illegal partition"
+        sys_oserr_entry         78, "Bad system area"
         sys_oserr_sentinel      "Unknown error"
diff --git a/libsrc/cbm/oserror.s b/libsrc/cbm/oserror.s
index c68830a51..872c75912 100644
--- a/libsrc/cbm/oserror.s
+++ b/libsrc/cbm/oserror.s
@@ -1,6 +1,6 @@
 ;
 ; 2000-05-17, Ullrich von Bassewitz
-; 2014-05-26, Greg King
+; 2014-05-28, Greg King
 ;
 ; int __fastcall__ _osmaperrno (unsigned char oserror);
 ; /* Map a system-specific error into a system-independent code. */
@@ -48,7 +48,7 @@ ErrTab:
         .byte  23, EIO          ; Checksum error
         .byte  24, EIO          ; Decode error
         .byte  25, EIO          ; Verify error
-        .byte  26, EACCES       ; Write protect on
+        .byte  26, EACCES       ; Write protected
         .byte  27, EIO          ; Checksum error
         .byte  28, EIO          ; Write overrun
         .byte  29, EBUSY        ; Disk ID mismatch
@@ -57,7 +57,8 @@ ErrTab:
         .byte  32, EINVAL       ; Command too long
         .byte  33, EINVAL       ; Invalid write filename
         .byte  34, EINVAL       ; No file given
-        .byte  39, ENOENT       ; File not found
+        .byte  39, ENOENT       ; System file not found
+        .byte  49, EACCES       ; Invalid format
         .byte  50, ESPIPE       ; Record not present
         .byte  51, ENOSPC       ; Overflow in record
         .byte  52, ENOSPC       ; File too large
@@ -74,5 +75,8 @@ ErrTab:
         .byte  72, ENOSPC       ; Disk full
         .byte  73, EACCES       ; DOS version mismatch
         .byte  74, ENODEV       ; Drive not ready
+        .byte  75, EIO          ; Format error
+        .byte  77, EINVAL       ; Illegal partition
+        .byte  78, EIO          ; Bad system area
 
 ErrTabSize = (* - ErrTab)