diff --git a/qa/rbd/krbd_discard_granularity.t b/qa/rbd/krbd_discard_granularity.t
index ceaf7657d25..8001786b0ab 100644
--- a/qa/rbd/krbd_discard_granularity.t
+++ b/qa/rbd/krbd_discard_granularity.t
@@ -1,4 +1,6 @@
 
+Default object size:
+
   $ rbd create --size 20M img
 
   $ DEV=$(sudo rbd map img)
@@ -38,3 +40,45 @@
   $ sudo rbd unmap $DEV
 
   $ rbd rm --no-progress img
+
+Custom object size:
+
+  $ rbd create --size 20M --object-size 1M img
+
+  $ DEV=$(sudo rbd map img)
+  $ blockdev --getiomin $DEV
+  65536
+  $ blockdev --getioopt $DEV
+  1048576
+  $ cat /sys/block/${DEV#/dev/}/queue/discard_granularity
+  65536
+  $ sudo rbd unmap $DEV
+
+  $ DEV=$(sudo rbd map -o alloc_size=512 img)
+  $ blockdev --getiomin $DEV
+  512
+  $ blockdev --getioopt $DEV
+  1048576
+  $ cat /sys/block/${DEV#/dev/}/queue/discard_granularity
+  512
+  $ sudo rbd unmap $DEV
+
+  $ DEV=$(sudo rbd map -o alloc_size=1048576 img)
+  $ blockdev --getiomin $DEV
+  1048576
+  $ blockdev --getioopt $DEV
+  1048576
+  $ cat /sys/block/${DEV#/dev/}/queue/discard_granularity
+  1048576
+  $ sudo rbd unmap $DEV
+
+  $ DEV=$(sudo rbd map -o alloc_size=2097152 img)
+  $ blockdev --getiomin $DEV
+  1048576
+  $ blockdev --getioopt $DEV
+  1048576
+  $ cat /sys/block/${DEV#/dev/}/queue/discard_granularity
+  1048576
+  $ sudo rbd unmap $DEV
+
+  $ rbd rm --no-progress img