diff --git a/debian/changelog b/debian/changelog
index 4b40e1a0..6c9f3078 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,8 @@ byobu (5.13) unreleased; urgency=low
     - simply speed up using perl
   * usr/bin/byobu: LP: #937175
     - check tput for 256 color support before defaulting to that in tmux mode
+  * usr/lib/byobu/disk_io: LP: #934893
+    - initialize the x1 value correctly
 
  -- Dustin Kirkland <kirkland@ubuntu.com>  Thu, 16 Feb 2012 23:58:36 -0600
 
diff --git a/usr/lib/byobu/disk_io b/usr/lib/byobu/disk_io
index 464b2eff..838696bd 100755
--- a/usr/lib/byobu/disk_io
+++ b/usr/lib/byobu/disk_io
@@ -52,16 +52,16 @@ __disk_io() {
 	esac
 	getdisk "$part"
 	local disk=${_RET}
-	local t2=`date +%s` t1=
+	local t2=$(date +%s) t1=
 	for i in "read" "write"; do
 		local cache="$BYOBU_RUN_DIR/cache.$BYOBU_BACKEND/disk.$i"
-		t1=`stat -c %Y "$cache"` 2>/dev/null || t1=0
+		t1=$(stat -c %Y "$cache") 2>/dev/null || t1=0
 		local unit="kB/s"
-		local rate= x1= x2= symbol= unit=
+		local rate=0 x1=0 x2=0 symbol= unit=
 		if [ $t2 -le $t1 ]; then
 			rate=0
 		else
-			[ -r "$cache" ] && read x1 < "$cache" || x1=0
+			[ -r "$cache" ] && read x1 < "$cache"
 			local a1= a2= a3= a4= a5= a6= a7= a8= a9= a10=
 			read a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 other < "/sys/block/$disk/stat"
 			if [ "$i" = "read" ]; then