diff --git a/include/spdk/bdev_module.h b/include/spdk/bdev_module.h
index de6e4a745..fc70278e1 100644
--- a/include/spdk/bdev_module.h
+++ b/include/spdk/bdev_module.h
@@ -968,7 +968,8 @@ const struct spdk_bdev_aliases_list *spdk_bdev_get_aliases(const struct spdk_bde
  * callback on read path.  The buffer will be freed automatically
  * on \c spdk_bdev_free_io() call. This call will never fail.
  * In case of lack of memory given callback \c cb will be deferred
- * until enough memory is freed.
+ * until enough memory is freed.  This function *must* be called
+ * from the thread issuing \c bdev_io.
  *
  * \param bdev_io I/O to allocate buffer for.
  * \param cb callback to be called when the buffer is allocated
diff --git a/lib/bdev/bdev.c b/lib/bdev/bdev.c
index 6b3af2559..713fc3e00 100644
--- a/lib/bdev/bdev.c
+++ b/lib/bdev/bdev.c
@@ -1227,6 +1227,7 @@ bdev_io_get_buf(struct spdk_bdev_io *bdev_io, uint64_t len)
 	uint64_t alignment, md_len;
 	void *buf;
 
+	assert(spdk_bdev_io_get_thread(bdev_io) == spdk_get_thread());
 	alignment = spdk_bdev_get_buf_align(bdev);
 	md_len = spdk_bdev_is_md_separate(bdev) ? bdev_io->u.bdev.num_blocks * bdev->md_len : 0;