diff --git a/http/src/microlog/rss.uppxml b/http/src/microlog/rss.uppxml
index 503ca1c..20a6ced 100644
--- a/http/src/microlog/rss.uppxml
+++ b/http/src/microlog/rss.uppxml
@@ -16,7 +16,7 @@ NOW_RFC_822="$(TZ=UT date +"%a, %d %b %Y %H:%M:%S UT")"
 
 #!
 for post in $POSTS; do
-POST_ID="${post::${#post}-17}"
+POST_ID="$(echo ${post} | cut -c1-$(( ${#post} - 17 )) )"
 . "${SRC}/microlog/${post}.args"
 DATE_PUBLISHED_RFC_822="$(TZ=UT date --date="$( echo "${POST_ID}" | cut -c1-10)" +"%a, %d %b %Y %H:%M:%S UT")"
 #!