diff --git a/ponydos.asm b/ponydos.asm
index 30ba7e1..ce9876f 100644
--- a/ponydos.asm
+++ b/ponydos.asm
@@ -328,7 +328,8 @@ shell_name db 'shell.bin', 0
 ;  ds:si = file name
 ;  dx = non-zero => do not create new file
 ; out:
-;  ax = LBA of first sector, 0 if no space left
+;  ax = LBA of first sector, 0 if no space left or if dx non-zero and the
+;       specified file was not found
 ;  cx = length in sectors
 ;  di = dirent address (in GLOBAL_DIRENTS)
 ; [Far calls only]
@@ -386,7 +387,7 @@ open_file:
 
 	.create_file:
 		test dx, dx
-		jnz .return
+		jnz .error
 
 		; TODO: zero out the sector for this file?
 		inc word [es:di]