diff --git a/plugins/disk/btrfs_device_usage b/plugins/disk/btrfs_device_usage
index 519e10d5..530e1568 100755
--- a/plugins/disk/btrfs_device_usage
+++ b/plugins/disk/btrfs_device_usage
@@ -155,9 +155,14 @@ def munin_values(fs):
 
     for this_device in devices:
         this_dev_info = fs.dev_info(this_device.devid)
-        usage = 100.0 * this_dev_info.bytes_used / this_dev_info.total_bytes
-        print("btrfs_percent_" + fsid + "_" + str(this_device.devid) +
-              ".value " + str(round(usage, 2)))
+        if this_dev_info.total_bytes > 0:
+            usage = 100.0 * this_dev_info.bytes_used / this_dev_info.total_bytes
+            print("btrfs_percent_" + fsid + "_" + str(this_device.devid) +
+                  ".value " + str(round(usage, 2)))
+        else:
+            print("btrfs_percent_" + fsid + "_" + str(this_device.devid) +
+                  ".value U")
+          
 
     print("")