diff --git a/src/xtgeo/xyz_common/_xyz_data.py b/src/xtgeo/xyz_common/_xyz_data.py
index 9f3cad1a7..293572c04 100644
--- a/src/xtgeo/xyz_common/_xyz_data.py
+++ b/src/xtgeo/xyz_common/_xyz_data.py
@@ -157,7 +157,7 @@ def zname(self):
         return self._zname
 
     def _infer_attr_dtypes(self):
-        """Return as dict on form {"X_UTME": "CONT", .... "FACIES": "DISC"}.
+        """Return as dict on form {"X_UTME": _AttrType.CONT, "FACIES": _AttrType.DISC}.
 
         There are some important restrictions:
         * The first 3 columns X Y Z) are always CONT, even if input appears as DISC.
@@ -173,8 +173,8 @@ def _infer_attr_dtypes(self):
         datatypes = {}
         for name, dtype in dlist.items():
             if name in self._attr_types:
+                # do not change already set attr_types
                 datatypes[name] = self._attr_types[name]
-
                 continue
 
             if name in (self._xname, self._yname, self._zname):