diff --git a/src/rougail/convert.py b/src/rougail/convert.py
index 200a2cd3a..21dcd94ff 100644
--- a/src/rougail/convert.py
+++ b/src/rougail/convert.py
@@ -590,7 +590,18 @@ class ParserVariable:
             extra_attrs = set(family_obj) - self.family_attrs
             if extra_attrs:
                 raise Exception(f"extra attrs ... {extra_attrs}")
-            if self.get_family_or_variable_type(family_obj) == "dynamic":
+            obj_type = self.get_family_or_variable_type(family_obj)
+            if obj_type is None:
+                # auto set type
+                if '_dynamic' in family_obj:
+                    dynamic = family_obj['_dynamic']
+                elif 'dynamic' in family_obj:
+                    dynamic = family_obj['dynamic']
+                else:
+                    dynamic = None
+                if isinstance(dynamic, (list, dict)):
+                    family_obj['type'] = obj_type = 'dynamic'
+            if obj_type == "dynamic":
                 family_is_dynamic = True
                 parent_dynamic = path
                 if '{{ suffix }}' not in name:
@@ -999,11 +1010,16 @@ class ParserVariable:
             calculations = calculations[0]
         else:
             calculations = calculations[1]
-        return (
-            attribute in calculations
-            and isinstance(value, dict)
-            and value.get("type") in CALCULATION_TYPES
-        )
+        if not isinstance(value, dict) or attribute not in calculations:
+            return False
+        if 'type' in value:
+            return value['type'] in CALCULATION_TYPES
+        # auto set type
+        typ = set(CALCULATION_TYPES) & set(value)
+        if len(typ) == 1:
+            value['type'] = list(typ)[0]
+            return True
+        return False
 
     def set_calculation(
         self,
@@ -1036,6 +1052,11 @@ class ParserVariable:
                 raise Exception("params must be a dict")
             params = []
             for key, val in calculation_object["params"].items():
+                if isinstance(val, dict) and "type" not in val:
+                    # auto set type
+                    param_typ = set(CALCULATION_TYPES) & set(val)
+                    if len(param_typ) == 1:
+                        val['type'] = list(param_typ)[0]
                 if not isinstance(val, dict) or "type" not in val:
                     param_typ = "any"
                     val = {
@@ -1214,6 +1235,8 @@ class RougailConvert(ParserVariable):
             objects,
             filename,
         )
+        if objects is None:
+            return
         self.parse_root_file(filename,
                              path,
                              version,
@@ -1268,6 +1291,8 @@ class RougailConvert(ParserVariable):
         filename: str,
     ) -> None:
         """version is mandatory in YAML file"""
+        if obj is None:
+            obj = {}
         for name in ["_version", "version"]:
             if name not in obj:
                 continue