diff --git a/app/controllers/administrateurs/groupe_instructeurs_controller.rb b/app/controllers/administrateurs/groupe_instructeurs_controller.rb
index db171b450..58d1cb379 100644
--- a/app/controllers/administrateurs/groupe_instructeurs_controller.rb
+++ b/app/controllers/administrateurs/groupe_instructeurs_controller.rb
@@ -215,7 +215,7 @@ module Administrateurs
       else
         file = group_csv_file.read
         base_encoding = CharlockHolmes::EncodingDetector.detect(file)
-        groupes_emails = ACSV::CSV.new(file.encode("UTF-8", base_encoding[:encoding], invalid: :replace, replace: ""), headers: true, header_converters: :downcase)
+        groupes_emails = ACSV::CSV.new_for_ruby3(file.encode("UTF-8", base_encoding[:encoding], invalid: :replace, replace: ""), headers: true, header_converters: :downcase)
           .map { |r| r.to_h.slice('groupe', 'email') }
 
         groupes_emails_has_keys = groupes_emails.first.has_key?("groupe") && groupes_emails.first.has_key?("email")
diff --git a/config/initializers/acsv.rb b/config/initializers/acsv.rb
new file mode 100644
index 000000000..3a24d2032
--- /dev/null
+++ b/config/initializers/acsv.rb
@@ -0,0 +1,16 @@
+require 'csv'
+
+# PR : https://github.com/wvengen/ruby-acsv/pull/3
+module ACSV
+  class CSV < ::CSV
+    def self.new_for_ruby3(data, options = {})
+      options[:col_sep] ||= ACSV::Detect.separator(data)
+      # because of the Separation of positional and keyword arguments in Ruby 3.0
+      # (https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/)
+      # instead of
+      # super(data, options)
+      # we do
+      ::CSV.new(data, **options)
+    end
+  end
+end