diff --git a/tests/md5.sh b/tests/md5.sh
index 4b95127701d0609a09c9603d05b0933ff76266dd..0b382b1a5eef5f73c4816ff42c98022cfc1d5116 100644
--- a/tests/md5.sh
+++ b/tests/md5.sh
@@ -1,6 +1,6 @@
 # try to find an md5 program
 
-if [ X"$(echo | md5sum 2> /dev/null)" != X ]; then
+if [ X"$(echo | md5sum -b 2> /dev/null)" != X ]; then
     do_md5sum() { md5sum -b $1; }
 elif [ X"$(echo | command md5 2> /dev/null)" != X ]; then
     do_md5sum() { command md5 $1 | sed 's#MD5 (\(.*\)) = \(.*\)#\2 *\1#'; }