diff --git a/src/lib_shell/bootstrap_pipeline.ml b/src/lib_shell/bootstrap_pipeline.ml
index 3c38609a7..75f52912a 100644
--- a/src/lib_shell/bootstrap_pipeline.ml
+++ b/src/lib_shell/bootstrap_pipeline.ml
@@ -26,7 +26,7 @@ type t = {
   fetched_headers:
     (Block_hash.t * Block_header.t) Lwt_pipe.t ;
   fetched_blocks:
-    (Block_hash.t * Block_header.t * Operation.t list list) Lwt_pipe.t ;
+    (Block_hash.t * Block_header.t * Operation.t list list tzresult Lwt.t) Lwt_pipe.t ;
   (* HACK, a worker should be able to return the 'error'. *)
   mutable errors: Error_monad.error list ;
 }
@@ -115,18 +115,20 @@ let rec operations_fetch_worker_loop pipeline =
     lwt_log_info "fetching operations of block %a from peer %a."
       Block_hash.pp_short hash
       P2p_peer.Id.pp_short pipeline.peer_id >>= fun () ->
-    map_p
-      (fun i ->
-         protect ~canceler:pipeline.canceler begin fun () ->
-           Distributed_db.Operations.fetch
-             ~timeout:pipeline.block_operations_timeout
-             pipeline.chain_db ~peer:pipeline.peer_id
-             (hash, i) header.shell.operations_hash
-         end)
-      (0 -- (header.shell.validation_passes - 1)) >>=? fun operations ->
-    lwt_log_info "fetched operations of block %a from peer %a."
-      Block_hash.pp_short hash
-      P2p_peer.Id.pp_short pipeline.peer_id >>= fun () ->
+    let operations =
+      map_p
+        (fun i ->
+           protect ~canceler:pipeline.canceler begin fun () ->
+             Distributed_db.Operations.fetch
+               ~timeout:pipeline.block_operations_timeout
+               pipeline.chain_db ~peer:pipeline.peer_id
+               (hash, i) header.shell.operations_hash
+           end)
+        (0 -- (header.shell.validation_passes - 1)) >>=? fun operations ->
+      lwt_log_info "fetched operations of block %a from peer %a."
+        Block_hash.pp_short hash
+        P2p_peer.Id.pp_short pipeline.peer_id >>= fun () ->
+      return operations in
     protect ~canceler:pipeline.canceler begin fun () ->
       Lwt_pipe.push pipeline.fetched_blocks
         (hash, header, operations) >>= return
@@ -159,6 +161,7 @@ let rec validation_worker_loop pipeline =
     lwt_log_info "requesting validation for block %a from peer %a."
       Block_hash.pp_short hash
       P2p_peer.Id.pp_short pipeline.peer_id >>= fun () ->
+    operations >>=? fun operations ->
     protect ~canceler:pipeline.canceler begin fun () ->
       Block_validator.validate
         ~canceler:pipeline.canceler
@@ -193,9 +196,9 @@ let create
     block_validator peer_id chain_db locator =
   let canceler = Lwt_canceler.create () in
   let fetched_headers =
-    Lwt_pipe.create ~size:(50, fun _ -> 1) () in
+    Lwt_pipe.create ~size:(1024, fun _ -> 1) () in
   let fetched_blocks =
-    Lwt_pipe.create ~size:(50, fun _ -> 1) () in
+    Lwt_pipe.create ~size:(128, fun _ -> 1) () in
   let pipeline = {
     canceler ;
     block_header_timeout ; block_operations_timeout ;