diff --git a/src/proto_016_PtMumbai/lib_delegate/state_transitions.ml b/src/proto_016_PtMumbai/lib_delegate/state_transitions.ml
index ab8f6d35d7bae5e8a2f84f5e81342a6f2b1030ef..1405bf4479a2896184bdec5d074b7aa1a9c6e1d1 100644
--- a/src/proto_016_PtMumbai/lib_delegate/state_transitions.ml
+++ b/src/proto_016_PtMumbai/lib_delegate/state_transitions.ml
@@ -783,6 +783,40 @@ let handle_expected_applied_proposal (state : Baking_state.t) =
         candidate
         preendorsement_qc
 
+module P_set = Set.Make (struct
+  type t = Kind.preendorsement Alpha_context.operation
+
+  let compare = Stdlib.compare
+end)
+
+module E_set = Set.Make (struct
+  type t = Kind.endorsement Alpha_context.operation
+
+  let compare = Stdlib.compare
+end)
+
+let assert_pqc loc pqc =
+  List.fold_left
+    (fun set op ->
+      if P_set.mem op set then (
+        Format.printf "wrong PQC at line %s@." loc ;
+        assert false)
+      else P_set.add op set)
+    P_set.empty
+    pqc
+  |> ignore
+
+let assert_eqc loc eqc =
+  List.fold_left
+    (fun set op ->
+      if E_set.mem op set then (
+        Format.printf "wrong EQC at line %s@." loc ;
+        assert false)
+      else E_set.add op set)
+    E_set.empty
+    eqc
+  |> ignore
+
 (* Hypothesis:
    - The state is not to be modified outside this module
      (NB: there are exceptions in Baking_actions: the corner cases
@@ -863,6 +897,7 @@ let step (state : Baking_state.t) (event : Baking_state.event) :
         Events.(emit new_valid_proposal_while_waiting_for_qc ()) >>= fun () ->
         handle_proposal ~is_proposal_applied:false state proposal
   | Awaiting_application, Prequorum_reached (candidate, preendorsement_qc) ->
+      assert_pqc __LOC__ preendorsement_qc ;
       may_register_early_prequorum state (candidate, preendorsement_qc)
   | Awaiting_preendorsements, Prequorum_reached (candidate, preendorsement_qc)
     ->
@@ -871,11 +906,16 @@ let step (state : Baking_state.t) (event : Baking_state.event) :
         candidate
         preendorsement_qc
   | Awaiting_endorsements, Quorum_reached (candidate, endorsement_qc) ->
+      assert_eqc __LOC__ endorsement_qc ;
       quorum_reached_when_waiting_endorsements state candidate endorsement_qc
   (* Unreachable cases *)
-  | Idle, (Prequorum_reached _ | Quorum_reached _)
-  | Awaiting_preendorsements, Quorum_reached _
-  | Awaiting_endorsements, Prequorum_reached _
-  | Awaiting_application, Quorum_reached _ ->
+  | Idle, Prequorum_reached (_, pqc)
+  | Awaiting_endorsements, Prequorum_reached (_, pqc) ->
+      assert_pqc __LOC__ pqc ;
+      do_nothing state
+  | Idle, Quorum_reached (_, eqc)
+  | Awaiting_preendorsements, Quorum_reached (_, eqc)
+  | Awaiting_application, Quorum_reached (_, eqc) ->
+      assert_eqc __LOC__ eqc ;
       (* This cannot/should not happen *)
       do_nothing state
diff --git a/src/proto_016_PtMumbai/lib_delegate/test/mockup_simulator/faked_daemon.ml b/src/proto_016_PtMumbai/lib_delegate/test/mockup_simulator/faked_daemon.ml
index 1319d3df51d97f72bece6925b7d5fad5e1c41150..6de60c59883feac81c2b9bf5ca1898e0f8786d9b 100644
--- a/src/proto_016_PtMumbai/lib_delegate/test/mockup_simulator/faked_daemon.ml
+++ b/src/proto_016_PtMumbai/lib_delegate/test/mockup_simulator/faked_daemon.ml
@@ -16,7 +16,8 @@ module Baker = struct
     let canceler = Lwt_canceler.create () in
     let on_error (err : error trace) =
       Lwt_canceler.cancel canceler >>= fun _ ->
-      failwith "%a" Error_monad.pp_print_trace err
+      Format.printf "%a" Error_monad.pp_print_trace err ;
+      Lwt_exit.exit_and_raise 1
     in
     Baking_scheduling.run
       cctxt
diff --git a/src/proto_alpha/lib_delegate/state_transitions.ml b/src/proto_alpha/lib_delegate/state_transitions.ml
index 9df396e48fb5a48564c4e4e31fde53218ace38e2..d33335e4a20ab7ac21c18137a641f39afb86e9fb 100644
--- a/src/proto_alpha/lib_delegate/state_transitions.ml
+++ b/src/proto_alpha/lib_delegate/state_transitions.ml
@@ -800,6 +800,40 @@ let handle_expected_applied_proposal (state : Baking_state.t) =
         candidate
         preendorsement_qc
 
+module P_set = Set.Make (struct
+  type t = Kind.preendorsement Alpha_context.operation
+
+  let compare = Stdlib.compare
+end)
+
+module E_set = Set.Make (struct
+  type t = Kind.endorsement Alpha_context.operation
+
+  let compare = Stdlib.compare
+end)
+
+let assert_pqc loc pqc =
+  List.fold_left
+    (fun set op ->
+      if P_set.mem op set then (
+        Format.printf "wrong PQC at line %s@." loc ;
+        assert false)
+      else P_set.add op set)
+    P_set.empty
+    pqc
+  |> ignore
+
+let assert_eqc loc eqc =
+  List.fold_left
+    (fun set op ->
+      if E_set.mem op set then (
+        Format.printf "wrong EQC at line %s@." loc ;
+        assert false)
+      else E_set.add op set)
+    E_set.empty
+    eqc
+  |> ignore
+
 (* Hypothesis:
    - The state is not to be modified outside this module
      (NB: there are exceptions in Baking_actions: the corner cases
@@ -880,6 +914,7 @@ let step (state : Baking_state.t) (event : Baking_state.event) :
         Events.(emit new_valid_proposal_while_waiting_for_qc ()) >>= fun () ->
         handle_proposal ~is_proposal_applied:false state proposal
   | Awaiting_application, Prequorum_reached (candidate, preendorsement_qc) ->
+      assert_pqc __LOC__ preendorsement_qc ;
       may_register_early_prequorum state (candidate, preendorsement_qc)
   | Awaiting_preendorsements, Prequorum_reached (candidate, preendorsement_qc)
     ->
@@ -888,11 +923,16 @@ let step (state : Baking_state.t) (event : Baking_state.event) :
         candidate
         preendorsement_qc
   | Awaiting_endorsements, Quorum_reached (candidate, endorsement_qc) ->
+      assert_eqc __LOC__ endorsement_qc ;
       quorum_reached_when_waiting_endorsements state candidate endorsement_qc
   (* Unreachable cases *)
-  | Idle, (Prequorum_reached _ | Quorum_reached _)
-  | Awaiting_preendorsements, Quorum_reached _
-  | Awaiting_endorsements, Prequorum_reached _
-  | Awaiting_application, Quorum_reached _ ->
+  | Idle, Quorum_reached (_, eqc)
+  | Awaiting_preendorsements, Quorum_reached (_, eqc)
+  | Awaiting_application, Quorum_reached (_, eqc) ->
+      assert_eqc __LOC__ eqc ;
+      do_nothing state
+  | Idle, Prequorum_reached (_, pqc)
+  | Awaiting_endorsements, Prequorum_reached (_, pqc) ->
       (* This cannot/should not happen *)
+      assert_pqc __LOC__ pqc ;
       do_nothing state
diff --git a/src/proto_alpha/lib_delegate/test/mockup_simulator/faked_daemon.ml b/src/proto_alpha/lib_delegate/test/mockup_simulator/faked_daemon.ml
index 1319d3df51d97f72bece6925b7d5fad5e1c41150..6de60c59883feac81c2b9bf5ca1898e0f8786d9b 100644
--- a/src/proto_alpha/lib_delegate/test/mockup_simulator/faked_daemon.ml
+++ b/src/proto_alpha/lib_delegate/test/mockup_simulator/faked_daemon.ml
@@ -16,7 +16,8 @@ module Baker = struct
     let canceler = Lwt_canceler.create () in
     let on_error (err : error trace) =
       Lwt_canceler.cancel canceler >>= fun _ ->
-      failwith "%a" Error_monad.pp_print_trace err
+      Format.printf "%a" Error_monad.pp_print_trace err ;
+      Lwt_exit.exit_and_raise 1
     in
     Baking_scheduling.run
       cctxt