diff --git a/requirements.txt b/requirements.txt
index 2f58679..3d083a4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,5 @@
-Django>=2.2,<3.1
+Django>=3.0,<3.2
 tabimport>=0.4.0
-openpyxl==2.4.9
-xlrd
+openpyxl==3.0.5
 reportlab
 django-summernote==0.8.11.6
diff --git a/stages/admin.py b/stages/admin.py
index ef40fa4..c7219b0 100644
--- a/stages/admin.py
+++ b/stages/admin.py
@@ -3,6 +3,7 @@ from copy import deepcopy
 
 from django import forms
 from django.contrib import admin
+from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME
 from django.contrib.auth.admin import GroupAdmin as AuthGroupAdmin
 from django.contrib.auth.models import Group
 from django.db import models
@@ -22,7 +23,7 @@ from .views.export import OpenXMLExport
 def print_charge_sheet(modeladmin, request, queryset):
     return HttpResponseRedirect(
         reverse('print-charge-sheet') + '?ids=%s' % ",".join(
-            request.POST.getlist(admin.ACTION_CHECKBOX_NAME)
+            request.POST.getlist(ACTION_CHECKBOX_NAME)
         )
     )
 print_charge_sheet.short_description = "Imprimer les feuilles de charge"
diff --git a/stages/views/export.py b/stages/views/export.py
index 23adf9d..81c27de 100644
--- a/stages/views/export.py
+++ b/stages/views/export.py
@@ -1,5 +1,6 @@
 from collections import OrderedDict
 from datetime import date
+from tempfile import NamedTemporaryFile
 
 from django.conf import settings
 from django.db.models import Q, Sum
@@ -8,7 +9,6 @@ from django.http import HttpResponse
 from openpyxl import Workbook
 from openpyxl.styles import Font
 from openpyxl.utils import get_column_letter
-from openpyxl.writer.excel import save_virtual_workbook
 
 from ..models import (
     Availability, CorpContact, Corporation, Course, Section, Student, Teacher,
@@ -42,11 +42,15 @@ class OpenXMLExport:
             if col_widths:
                 self.ws.column_dimensions[get_column_letter(col_idx)].width = col_widths[col_idx - 1]
         self.row_idx += 1
-        
+
     def get_http_response(self, filename_base):
-        response = HttpResponse(save_virtual_workbook(self.wb), content_type=openxml_contenttype)
-        response['Content-Disposition'] = 'attachment; filename=%s_%s.xlsx' % (
-            filename_base, date.strftime(date.today(), '%Y-%m-%d'))
+        with NamedTemporaryFile() as tmp:
+            self.wb.save(tmp.name)
+            tmp.seek(0)
+            response = HttpResponse(tmp, content_type=openxml_contenttype)
+            response['Content-Disposition'] = 'attachment; filename=%s_%s.xlsx' % (
+                filename_base, date.strftime(date.today(), '%Y-%m-%d')
+            )
         return response
 
 
@@ -197,8 +201,8 @@ def _ratio_Ede_Ase_Assc():
     tot_asscfe = Course.objects.filter(imputation='ASSCFE').aggregate(Sum('period'))['period__sum'] or 0
     tot_mps = Course.objects.filter(imputation='MPS').aggregate(Sum('period'))['period__sum'] or 0
     asscfe_ratio = 1 if tot_asscfe + tot_mps == 0 else tot_asscfe / (tot_asscfe + tot_mps)
-    
-    return {'edepe':edepe_ratio, 'asefe':asefe_ratio, 'asscfe': asscfe_ratio}
+
+    return {'edepe': edepe_ratio, 'asefe': asefe_ratio, 'asscfe': asscfe_ratio}
 
 
 def imputations_export(request):