diff --git a/app/policies/champ_policy.rb b/app/policies/champ_policy.rb
index 81d2eb11b..2df555cbd 100644
--- a/app/policies/champ_policy.rb
+++ b/app/policies/champ_policy.rb
@@ -5,16 +5,18 @@ class ChampPolicy < ApplicationPolicy
         return scope.none
       end
 
-      # Users can access public champs on their own dossiers.
-      resolved_scope = scope
+      # The join must be the same for all elements of the WHERE clause.
+      joined_scope = scope
         .left_outer_joins(dossier: { groupe_instructeur: [:instructeurs] })
+
+      # Users can access public champs on their own dossiers.
+      resolved_scope = joined_scope
         .where('dossiers.user_id': user.id, private: false)
 
       if instructeur.present?
         # Additionnaly, instructeurs can access private champs
         # on dossiers they are allowed to instruct.
-        instructeur_clause = scope
-          .left_outer_joins(dossier: { groupe_instructeur: [:instructeurs] })
+        instructeur_clause = joined_scope
           .where('instructeurs.id': instructeur.id, private: true)
         resolved_scope = resolved_scope.or(instructeur_clause)
       end