diff --git a/bin/fproc_cache.rc b/bin/fproc_cache.rc
index 5a3b0eb..6d419e4 100755
--- a/bin/fproc_cache.rc
+++ b/bin/fproc_cache.rc
@@ -9,9 +9,10 @@ score=`{{tee $tmpfile || exit 1} | sha1sum}
 cachedir=/tmp/fproc_cache/$score
 mkdir -p $cachedir >[2]/dev/null
 
-if(test -f $cachedir/$proc)
+if(test -s $cachedir/$proc)
     cat $cachedir/$proc
 if not {
+    # XXX For reliability mv should not be called unless both $proc and tee suceed
     $proc < $tmpfile | tee $cachedir/$pid
     mv $cachedir/$pid $cachedir/$proc
 }