diff --git a/app/scodoc/sco_bac.py b/app/scodoc/sco_bac.py
index ce00d96c..6f316a10 100644
--- a/app/scodoc/sco_bac.py
+++ b/app/scodoc/sco_bac.py
@@ -132,19 +132,29 @@ BACS_S = {t[0]: t[2:] for t in _BACS}
 
 class Baccalaureat:
     def __init__(self, bac, specialite=""):
-        self.bac = bac
-        self.specialite = specialite
-        self._abbrev, self._type = BACS_SSP.get((bac, specialite), (None, None))
+        self.bac = bac or ""
+        self.specialite = specialite or ""
+        self._abbrev, self._type = BACS_SSP.get(
+            (self.bac, self.specialite), (None, None)
+        )
         # Parfois, la specialite commence par la serie: essaye
-        if self._type is None and specialite and specialite.startswith(bac):
-            specialite = specialite[len(bac) :].strip(" -")
-            self._abbrev, self._type = BACS_SSP.get((bac, specialite), (None, None))
+        if (
+            self._type is None
+            and self.specialite
+            and self.specialite.startswith(self.bac)
+        ):
+            specialite = self.specialite[len(self.bac) :].strip(" -")
+            self._abbrev, self._type = BACS_SSP.get(
+                (self.bac, specialite), (None, None)
+            )
         # Cherche la forme serie specialite
         if self._type is None and specialite:
-            self._abbrev, self._type = BACS_S.get(bac + " " + specialite, (None, None))
+            self._abbrev, self._type = BACS_S.get(
+                self.bac + " " + specialite, (None, None)
+            )
         # Cherche avec juste le bac, sans specialite
         if self._type is None:
-            self._abbrev, self._type = BACS_S.get(bac, (None, None))
+            self._abbrev, self._type = BACS_S.get(self.bac, (None, None))
 
     def abbrev(self):
         "abbreviation for this bac"