diff --git a/app/models/champ.rb b/app/models/champ.rb
index da1919a83..505bfaa97 100644
--- a/app/models/champ.rb
+++ b/app/models/champ.rb
@@ -148,7 +148,7 @@ class Champ < ApplicationRecord
   # predictable input name.
   def input_name
     if parent_id
-      "#{parent.input_name}[#{champs_attributes_accessor}][#{id}]"
+      "#{parent.input_name}[champs_attributes][#{id}]"
     else
       "dossier[#{champs_attributes_accessor}][#{id}]"
     end
diff --git a/spec/models/champ_spec.rb b/spec/models/champ_spec.rb
index b256a04d9..3391ec4f0 100644
--- a/spec/models/champ_spec.rb
+++ b/spec/models/champ_spec.rb
@@ -602,5 +602,25 @@ describe Champ do
         expect(champ.reload.data).to eq data
       end
     end
+
+    context "#input_name" do
+      let(:champ) { create(:champ_text) }
+      it { expect(champ.input_name).to eq "dossier[champs_attributes][#{champ.id}]" }
+
+      context "when private" do
+        let(:champ) { create(:champ_text, private: true) }
+        it { expect(champ.input_name).to eq "dossier[champs_private_attributes][#{champ.id}]" }
+      end
+
+      context "when has parent" do
+        let(:champ) { create(:champ_text, parent: create(:champ_text)) }
+        it { expect(champ.input_name).to eq "dossier[champs_attributes][#{champ.parent_id}][champs_attributes][#{champ.id}]" }
+      end
+
+      context "when has private parent" do
+        let(:champ) { create(:champ_text, private: true, parent: create(:champ_text, private: true)) }
+        it { expect(champ.input_name).to eq "dossier[champs_private_attributes][#{champ.parent_id}][champs_attributes][#{champ.id}]" }
+      end
+    end
   end
 end