diff --git a/src/validators/i18n/fr.py b/src/validators/i18n/fr.py
index 5552ef61..04d8cd9e 100644
--- a/src/validators/i18n/fr.py
+++ b/src/validators/i18n/fr.py
@@ -102,14 +102,14 @@ def fr_ssn(value: str):
     if department != "99" and not fr_department(department):
         # 99 stands for foreign born people
         return False
-    if control_key is None:
-        # no control key provided, no additional check needed
-        return True
     if len(department) == len(groups[4]):
         # if the department number is 3 digits long (overseas departments),
         # the town number must be 2 digits long
         # and vice versa
         return False
+    if control_key is None:
+        # no control key provided, no additional check needed
+        return True
     if department in ("2A", "2B"):
         # Corsica's department numbers are not in the same range as the others
         # thus 2A and 2B are replaced by 19 and 18 respectively to compute the control key
diff --git a/tests/i18n/test_fr.py b/tests/i18n/test_fr.py
index f25c87c5..9727a069 100644
--- a/tests/i18n/test_fr.py
+++ b/tests/i18n/test_fr.py
@@ -21,6 +21,9 @@
         ("2 99 05 2A 202 817 58",),
         ("2 99 05 2B 202 817 85",),
         ("2 99 05 971 12 817 70",),
+        ("2 99 05 971 12 817",),  # overseas department without control key
+        ("2 99 05 2A 202 817",),  # Corsica without control key
+        ("2 99 05 99 202 817",),  # foreign birthplace without control key
     ],
 )
 def test_returns_true_on_valid_ssn(value: str):
@@ -41,7 +44,10 @@ def test_returns_true_on_valid_ssn(value: str):
         ("1 84 12 00 451 089",),  # invalid department
         ("1 84 12 2C 451 089",),
         ("1 84 12 98 451 089",),  # invalid department
-        # ("1 84 12 971 451 089",), # ?
+        ("1 84 12 971 451 089",),  # three-digit department needs two-digit town
+        ("1 84 12 76 45 089",),  # two-digit department needs three-digit town
+        ("1 84 12 2A 45 089",),
+        ("1 84 12 99 45 089",),
     ],
 )
 def test_returns_failed_validation_on_invalid_ssn(value: str):