diff --git a/block.c b/block.c
index 6191ac1f440..44d59362d68 100644
--- a/block.c
+++ b/block.c
@@ -6924,6 +6924,10 @@ bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
     return true;
 }
 
+/*
+ * Must not be called while holding the lock of an AioContext other than the
+ * current one.
+ */
 void bdrv_img_create(const char *filename, const char *fmt,
                      const char *base_filename, const char *base_fmt,
                      char *options, uint64_t img_size, int flags, bool quiet,
diff --git a/blockdev.c b/blockdev.c
index d2f80b0386f..ebf952cd218 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1507,10 +1507,14 @@ static void external_snapshot_prepare(BlkActionState *common,
                 goto out;
             }
             bdrv_refresh_filename(state->old_bs);
+
+            aio_context_release(aio_context);
             bdrv_img_create(new_image_file, format,
                             state->old_bs->filename,
                             state->old_bs->drv->format_name,
                             NULL, size, flags, false, &local_err);
+            aio_context_acquire(aio_context);
+
             if (local_err) {
                 error_propagate(errp, local_err);
                 goto out;