diff --git a/app/controllers/gestionnaires/dossiers_controller.rb b/app/controllers/gestionnaires/dossiers_controller.rb
index f8d02a855..6584b3af3 100644
--- a/app/controllers/gestionnaires/dossiers_controller.rb
+++ b/app/controllers/gestionnaires/dossiers_controller.rb
@@ -92,8 +92,12 @@ module Gestionnaires
     end
 
     def repasser_en_construction
-      dossier.repasser_en_construction!(current_gestionnaire)
-      flash.notice = 'Dossier repassé en construction.'
+      if dossier.en_construction?
+        flash.notice = 'Le dossier est déjà en construction.'
+      else
+        dossier.repasser_en_construction!(current_gestionnaire)
+        flash.notice = 'Dossier repassé en construction.'
+      end
 
       render partial: 'state_button_refresh', locals: { dossier: dossier }
     end
diff --git a/spec/controllers/gestionnaires/dossiers_controller_spec.rb b/spec/controllers/gestionnaires/dossiers_controller_spec.rb
index 26365a6c7..eeee2ee5d 100644
--- a/spec/controllers/gestionnaires/dossiers_controller_spec.rb
+++ b/spec/controllers/gestionnaires/dossiers_controller_spec.rb
@@ -128,21 +128,27 @@ describe Gestionnaires::DossiersController, type: :controller do
   end
 
   describe '#repasser_en_construction' do
+    let(:dossier) { create(:dossier, :en_instruction, procedure: procedure) }
+
     before do
-      dossier.en_instruction!
       sign_in gestionnaire
+      post :repasser_en_construction,
+        params: { procedure_id: procedure.id, dossier_id: dossier.id },
+        format: 'js'
     end
 
-    subject { post :repasser_en_construction, params: { procedure_id: procedure.id, dossier_id: dossier.id }, format: 'js' }
+    it { expect(dossier.reload.state).to eq(Dossier.states.fetch(:en_construction)) }
+    it { expect(response).to have_http_status(:ok) }
+    it { expect(response.body).to include('.state-button') }
 
-    it 'change state to en_construction' do
-      subject
+    context 'when the dossier has already been put en_construction' do
+      let(:dossier) { create(:dossier, :en_construction, procedure: procedure) }
 
-      dossier.reload
-      expect(dossier.state).to eq(Dossier.states.fetch(:en_construction))
+      it 'warns about the error, but doesn’t raise' do
+        expect(dossier.reload.state).to eq(Dossier.states.fetch(:en_construction))
+        expect(response).to have_http_status(:ok)
+      end
     end
-
-    it { expect(subject.body).to include('.state-button') }
   end
 
   describe '#terminer' do