diff --git a/doc/bugs/git_annex_fsck_on_btrfs_devices.mdwn b/doc/bugs/git_annex_fsck_on_btrfs_devices.mdwn
new file mode 100644
index 0000000000..1ad2f65f94
--- /dev/null
+++ b/doc/bugs/git_annex_fsck_on_btrfs_devices.mdwn
@@ -0,0 +1,14 @@
+### Please describe the problem.
+btrfs automatically validates checksums when data is read. If a checksum fails, instead of giving the corrupted file contents, the read will throw an I/O error. In result, it seems that git-annex fsck will not recognize the file as faulty, and will instead fail with a sha1sum parse error, without dropping the corresponding file as “bad”.
+
+[[!format sh """
+git annex fsck file
+fsck file (checksum...)
+sha1sum: .git/annex/objects/…: Input/output error
+git-annex: sha1sum parse error
+# End of transcript or log.
+"""]]
+
+### What version of git-annex are you using? On what operating system?
+git-annex 5.20150508
+linux 4.0.4