diff --git a/src/lib_shell/bootstrap_pipeline.ml b/src/lib_shell/bootstrap_pipeline.ml
index 323f8b3d5..021e8f44e 100644
--- a/src/lib_shell/bootstrap_pipeline.ml
+++ b/src/lib_shell/bootstrap_pipeline.ml
@@ -35,7 +35,7 @@ let assert_acceptable_header pipeline
     ?(first = false) hash (header : Block_header.t) =
   let chain_state = Distributed_db.chain_state pipeline.chain_db in
   fail_unless
-    (Time.(now () >= header.shell.timestamp))
+    (Time.(add (now ()) 15L >= header.shell.timestamp))
     (Future_block_header hash) >>=? fun () ->
   State.Chain.checkpoint chain_state >>= fun (level, checkpoint) ->
   fail_when
diff --git a/src/lib_shell/distributed_db.ml b/src/lib_shell/distributed_db.ml
index d77eea659..eff7551ec 100644
--- a/src/lib_shell/distributed_db.ml
+++ b/src/lib_shell/distributed_db.ml
@@ -494,7 +494,7 @@ module P2p_reader = struct
           (* TODO Kick *)
           P2p.greylist_peer global_db.p2p state.gid ;
           Lwt.return_unit
-        end else if Time.(now () < head.shell.timestamp) then begin
+        end else if Time.(add (now ()) 15L < head.shell.timestamp) then begin
           (* TODO some penalty *)
           lwt_log_notice "Received future block %a from peer %a."
             Block_hash.pp_short (Block_header.hash head)
@@ -545,7 +545,7 @@ module P2p_reader = struct
           (* TODO Kick *)
           P2p.greylist_peer global_db.p2p state.gid ;
           Lwt.return_unit
-        end else if Time.(now () < header.shell.timestamp) then begin
+        end else if Time.(add (now ()) 15L < header.shell.timestamp) then begin
           (* TODO some penalty *)
           lwt_log_notice "Received future block %a from peer %a."
             Block_hash.pp_short head