diff --git a/lib/cros_sdk_lib.py b/lib/cros_sdk_lib.py
index 8b257e7..358706c 100644
--- a/lib/cros_sdk_lib.py
+++ b/lib/cros_sdk_lib.py
@@ -394,7 +394,18 @@
   # unmount it.
   vg_name, _ = FindChrootMountSource(chroot, proc_mounts=proc_mounts)
 
-  osutils.UmountTree(chroot)
+  try:
+    osutils.UmountTree(chroot)
+  except cros_build_lib.RunCommandError as e:
+    # TODO(lamontjones): Dump some information to help find the process still
+    # inside the chroot, causing crbug.com/923432.  In the end, this is likely
+    # to become fuser -k.
+    fuser = cros_build_lib.SudoRunCommand(['fuser', chroot], error_code_ok=True)
+    lsof = cros_build_lib.SudoRunCommand(['lsof', chroot], error_code_ok=True)
+    ps = cros_build_lib.RunCommand(['ps', 'auxf'], error_code_ok=True)
+    raise Error(
+        'Umount failed: %s.\nfuser output=%s\nlsof output=%s\nps output=%s\n',
+        e.result.error, fuser.output, lsof.output, ps.output)
 
   # Find the loopback device by either matching the VG or the image.
   chroot_dev = None