diff --git a/app/models/concerns/tags_substitution_concern.rb b/app/models/concerns/tags_substitution_concern.rb
index 0ba9b9bb5..d1d4df5df 100644
--- a/app/models/concerns/tags_substitution_concern.rb
+++ b/app/models/concerns/tags_substitution_concern.rb
@@ -19,6 +19,7 @@ module TagsSubstitutionConcern
         .sub(/[[:space:]]+$/, '')
         .gsub(/[[:space:]]/, ' ')
         .gsub(' ', ' ')
+        .gsub(/--/, '__')
     end
 
     define_combinator :doc do
diff --git a/spec/models/concern/tags_substitution_concern_spec.rb b/spec/models/concern/tags_substitution_concern_spec.rb
index 6dbc7c869..e50ecfd70 100644
--- a/spec/models/concern/tags_substitution_concern_spec.rb
+++ b/spec/models/concern/tags_substitution_concern_spec.rb
@@ -211,7 +211,7 @@ describe TagsSubstitutionConcern, type: :model do
       end
 
       context 'and they are used in the template' do
-        let(:template) { "--bon pote -- c'est top--" }
+        let(:template) { "--bon pote __ c'est top--" }
 
         context 'and their value in the dossier are not nil' do
           before do