diff --git a/tools/testupdate.sh b/tools/testupdate.sh
index f530b8a..a5d5513 100755
--- a/tools/testupdate.sh
+++ b/tools/testupdate.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # Update the reference test data to match what is actually produced
 # This should only be executed after manually verifying that the
@@ -8,6 +8,12 @@
 #
 #
 
+# Remove elements that do not affect the structure of a file
+remove_trivia()
+{
+	grep -v 'Generated by' "$@"
+}
+
 for i in dot umldoc
 do
 	git ls-files testdata/*-ref |
@@ -15,7 +21,7 @@ do
 	while read refname outname
 	do
 		if [ -r "$outname" -a -r "$outname" ] && \
-			! cmp -s $refname $outname
+		  ! diff <(remove_trivia $refname) <(remove_trivia $outname) >/dev/null
 		then
 			cp $outname $refname
 		fi