diff --git a/src/lib_smart_rollup_node/layer1.ml b/src/lib_smart_rollup_node/layer1.ml
index 974a26c7742e93fced1524ae8f1b0ef22acf82f8..7a3a1157e17e01681d4a9bf582a2104b2d5c2a96 100644
--- a/src/lib_smart_rollup_node/layer1.ml
+++ b/src/lib_smart_rollup_node/layer1.ml
@@ -212,14 +212,35 @@ let fetch_tezos_block (fetch_rpc : fetch_block_rpc) extract_header
     cache_shell_header l1_ctxt hash (extract_header block) ;
     return block
   in
-  let* block = Blocks_cache.bind_or_put blocks_cache hash fetch Lwt.return in
+  let*! block = Blocks_cache.bind_or_put blocks_cache hash fetch Lwt.return in
+  (* TODO: https://gitlab.com/tezos/tezos/-/issues/6292
+     Consider cleaner ways to "prefetch" tezos blocks:
+     - know before where are protocol boundaries
+     - prefetch blocks in binary form *)
   let is_of_expected_protocol =
-    try
-      let (_ : Block_header.shell_header) = extract_header block in
-      true
-    with _ -> false
+    match block with
+    | Error
+        (Tezos_rpc_http.RPC_client_errors.(
+           Request_failed {error = Unexpected_content _; _})
+        :: _) ->
+        (* The promise cached failed to parse the block because it was for the
+           wrong protocol. *)
+        false
+    | Error _ ->
+        (* The promise cached failed for another reason. *)
+        true
+    | Ok block -> (
+        (* We check if we are able to extract the header, which inherently
+           ensures that we are in the correct case of type {!type:block}. *)
+        try
+          let (_ : Block_header.shell_header) = extract_header block in
+          true
+        with _ ->
+          (* This can happen if the blocks for two protocols have the same
+             binary representation. *)
+          false)
   in
-  if is_of_expected_protocol then return block
+  if is_of_expected_protocol then Lwt.return block
   else
     (* It is possible for a value stored in the cache to have been parsed
        with the wrong protocol code because:
diff --git a/src/lib_smart_rollup_node/refutation_coordinator.ml b/src/lib_smart_rollup_node/refutation_coordinator.ml
index 1a53e69bfaa0d9a542254b5d88dc592fdd2bfdd9..c981947b4cae0dbefd10eca1d5ff714de5229b18 100644
--- a/src/lib_smart_rollup_node/refutation_coordinator.ml
+++ b/src/lib_smart_rollup_node/refutation_coordinator.ml
@@ -149,7 +149,8 @@ module Handlers = struct
       =
    fun w request ->
     let state = Worker.state w in
-    match request with Request.Process b -> on_process b state
+    match request with
+    | Request.Process b -> protect @@ fun () -> on_process b state
 
   type launch_error = error trace
 
diff --git a/src/lib_smart_rollup_node/refutation_player.ml b/src/lib_smart_rollup_node/refutation_player.ml
index c615511eb3b727db26bdcd6681111c571b33e26e..0eca27506b7b0624fccba91664aef141dd08778a 100644
--- a/src/lib_smart_rollup_node/refutation_player.ml
+++ b/src/lib_smart_rollup_node/refutation_player.ml
@@ -70,8 +70,9 @@ module Handlers = struct
    fun w request ->
     let state = Worker.state w in
     match request with
-    | Request.Play game -> on_play game state
-    | Request.Play_opening conflict -> on_play_opening conflict state
+    | Request.Play game -> protect @@ fun () -> on_play game state
+    | Request.Play_opening conflict ->
+        protect @@ fun () -> on_play_opening conflict state
 
   type launch_error = error trace