diff --git a/stages/models.py b/stages/models.py
index 195d7b2..a1d182f 100644
--- a/stages/models.py
+++ b/stages/models.py
@@ -78,6 +78,7 @@ class Teacher(models.Model):
     def calc_activity(self):
         """
         Return a dictionary of calculations relative to teacher courses.
+        Store plus/minus periods to self.next_report.
         """
         mandats = self.course_set.filter(subject__startswith='#')
         ens = self.course_set.exclude(subject__startswith='#')
@@ -91,10 +92,11 @@ class Teacher(models.Model):
         # Special situations triggering reporting (positive or negative) hours for next year:
         #  - full-time teacher with a total charge under 100%
         #  - teachers with a total charge over 100%
+        self.next_report = 0
         if (self.rate == 100 and tot_paye < max_periods) or (tot_paye > max_periods):
             tot_paye = max_periods
-            self.next_report = tot_paye - tot_trav
-            self.save()
+            self.next_report = tot_trav - tot_paye
+        self.save()
 
         return {
             'mandats': mandats,
diff --git a/stages/tests.py b/stages/tests.py
index 12d6505..aa7c7df 100644
--- a/stages/tests.py
+++ b/stages/tests.py
@@ -173,7 +173,8 @@ class TeacherTests(TestCase):
     def setUpTestData(cls):
         User.objects.create_superuser('me', 'me@example.org', 'mepassword')
         cls.teacher = Teacher.objects.create(
-            first_name='Jeanne', last_name='Dubois', birth_date='1974-08-08', rate=50.0
+            first_name='Jeanne', last_name='Dubois', birth_date='1974-08-08',
+            rate=50.0, next_report=1,
         )
         Course.objects.create(
             teacher=cls.teacher, period=8, subject='#ASE Colloque', imputation='ASSCFE',
@@ -213,6 +214,7 @@ class TeacherTests(TestCase):
         effective = self.teacher.calc_activity()
         del effective['mandats']
         self.assertEqual(effective, expected)
+        self.assertEqual(self.teacher.next_report, 0)
 
         # Test over max hours per year for a full time
         self.teacher.rate = 100.0
@@ -228,9 +230,9 @@ class TeacherTests(TestCase):
             'tot_formation': Teacher.MAX_FORMATION + 1,
             'tot_trav': Teacher.MAX_ENS_PERIODS + Teacher.MAX_FORMATION + 1 + 8,
             'tot_paye': Teacher.MAX_ENS_PERIODS + Teacher.MAX_FORMATION,
-            'report': -8 - 1,
+            'report': 8 + 1,
         })
-        self.assertEqual(self.teacher.next_report, -8 - 1)
+        self.assertEqual(self.teacher.next_report, 8 + 1)
 
         # Test below max hours per year for a full time
         crs.period = Teacher.MAX_ENS_PERIODS - 4 - 10
@@ -243,9 +245,9 @@ class TeacherTests(TestCase):
             'tot_formation': Teacher.MAX_FORMATION,
             'tot_trav': Teacher.MAX_ENS_PERIODS + Teacher.MAX_FORMATION + 8 - 10,
             'tot_paye': Teacher.MAX_ENS_PERIODS + Teacher.MAX_FORMATION,
-            'report': 2,
+            'report': -2,
         })
-        self.assertEqual(self.teacher.next_report, 2)
+        self.assertEqual(self.teacher.next_report, -2)
 
     def test_calc_imputations(self):
         result = self.teacher.calc_imputations()