diff --git a/notes_tools/tools/df_marks_manip.py b/notes_tools/tools/df_marks_manip.py
index b231370..379f608 100644
--- a/notes_tools/tools/df_marks_manip.py
+++ b/notes_tools/tools/df_marks_manip.py
@@ -7,7 +7,7 @@ from math import ceil, floor
 import logging
 logger = logging.getLogger(__name__)
 
-NOANSWER = "na"
+NOANSWER = "."
 NORATED = ""
 
 # Values manipulations
@@ -479,6 +479,10 @@ def digest_flat_df(flat_df):
     """
     df = flat_df.dropna(subset=["Note"])
 
+    df["Question"].fillna("", inplace = True)
+    df["Exercice"].fillna("", inplace = True)
+    df["Domaine"].fillna("", inplace = True)
+    df["Competence"].fillna("", inplace = True)
     df["Mark"] = compute_marks(df)
     df["Level"] = compute_level(df)
     df["Latex_rep"] = compute_latex_rep(df)
diff --git a/notes_tools/tools/extract.py b/notes_tools/tools/extract.py
index db2aaec..4636d3f 100644
--- a/notes_tools/tools/extract.py
+++ b/notes_tools/tools/extract.py
@@ -132,6 +132,11 @@ def extract_flat_marks(ws,
         flat = flat_df_students(sheet, students)
         flat_df = pd.concat([flat_df, flat])
 
+    flat_df["Question"].fillna("", inplace = True)
+    flat_df["Exercice"].fillna("", inplace = True)
+    flat_df["Commentaire"].fillna("", inplace = True)
+    flat_df["Competence"].fillna("", inplace = True)
+
     return flat_df