diff --git a/plugins/lxc/lxc-multigraph b/plugins/lxc/lxc-multigraph
index 177c681d..183fcc8f 100755
--- a/plugins/lxc/lxc-multigraph
+++ b/plugins/lxc/lxc-multigraph
@@ -269,7 +269,8 @@ EOF
       fi
       bps="U"
       if [ -r "/sys/class/net/$device/speed" ]; then
-         bps=$(($(cat "/sys/class/net/$device/speed") * 1000 * 1000))
+         megabit_per_second=$(cat "/sys/class/net/$device/speed")
+         bps=$((megabit_per_second * 1000 * 1000))
       fi
       cat <<EOF
 $(clean_fieldname "net__${n}_down").label $n