diff --git a/rom.ps b/rom.ps
index 6935645..748e6ea 100644
--- a/rom.ps
+++ b/rom.ps
@@ -4,7 +4,7 @@
 % MAME's emulation of the SAA5050 family.  To produce such an image,
 % use a command like this:
 %
-% gs -P -q -dSAFER -sDEVICE=bit -o saa5051.rom rom.ps
+% gs -P -q -dSAFER -sDEVICE=bit -o saa5051.rom -- rom.ps SAA5051
 %
 % The image can also be compared against images from other sources to
 % detect errors in one or other source.  Currently only the SAA5051
@@ -48,8 +48,10 @@
 << /HWResolution [ 72 72 ]
    /PageSize [ 8 960 ] >> setpagedevice
 /Bedstead findfont 10 scalefont setfont
-2 952 moveto
-/SAA5051 findencoding
-32 96 getinterval
-{ glyphshow -6 -10 rmoveto } forall
-showpage
+ARGUMENTS {
+    2 952 moveto
+    cvn findencoding
+    32 96 getinterval
+    { glyphshow -6 -10 rmoveto } forall
+    showpage
+} forall