<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: times new roman,new york,times,serif; font-size: 12pt; color: #000000'><pre style="color: rgb(0, 0, 0); font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;">The error shows up in debian (wheezy) or ubuntu texlive implemetations of MetaPost, where "dpkg -l |grep metapost" gives, in part,</pre><pre><font size="4">ii texlive-metapost 2012.20120611-5</font></pre><pre><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;"><br></span></pre><pre><span style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;">> I don't have the mpost 1.504, but the example works fine</span></pre><pre style="color: rgb(0, 0, 0); font-family: 'times new roman', 'new york', times, serif; font-size: 12pt;">> in TeX Live 2013 pretest with mpost 1.802.
>
> Best,
> Akira</pre></div></body></html>