diff --git a/python/obitools3/obidms/_obidmscolumn_qual.pyx b/python/obitools3/obidms/_obidmscolumn_qual.pyx
index 00d82ab..f8c4635 100644
--- a/python/obitools3/obidms/_obidmscolumn_qual.pyx
+++ b/python/obitools3/obidms/_obidmscolumn_qual.pyx
@@ -70,11 +70,16 @@ cdef class OBIDMS_column_qual(OBIDMS_column):
             free(value_b)
 
     cpdef set_str_line(self, index_t line_nb, object value):
+        cdef bytes value_b        
         if value is None :
             if obi_set_qual_char_with_elt_idx_and_col_p_in_view(self.view.pointer, (self.pointer)[0], line_nb, 0, OBIQual_char_NA) < 0:
                 raise Exception("Problem setting a value in a column")
         else :
-            if obi_set_qual_char_with_elt_idx_and_col_p_in_view(self.view.pointer, (self.pointer)[0], line_nb, 0, str2bytes(value)) < 0:
+            if type(value) == str:
+                value_b = str2bytes(value)
+            else :
+                value_b = value
+            if obi_set_qual_char_with_elt_idx_and_col_p_in_view(self.view.pointer, (self.pointer)[0], line_nb, 0, value_b) < 0:
                 raise Exception("Problem setting a value in a column")