diff --git a/prjxray/db.py b/prjxray/db.py
index daecc2ea..50ecc6a8 100644
--- a/prjxray/db.py
+++ b/prjxray/db.py
@@ -42,7 +42,7 @@ class Database(object):
         self.tile_segbits = {}
         self.site_types = {}
 
-        per_part_features = {}
+        self.required_features = {}
 
         for f in os.listdir(self.db_root):
             if f.endswith('.json') and f.startswith('tile_type_'):
@@ -97,23 +97,10 @@ class Database(object):
                         if len(line) > 0:
                             features.append(line)
 
-                    per_part_features[part] = set(features)
+                    self.required_features[part] = set(features)
 
         self.tile_types_obj = {}
 
-        # Find common required features for all supported parts
-        if len(per_part_features) > 0:
-            common_features = set.intersection(*per_part_features.values())
-            for features in per_part_features.values():
-                features -= common_features
-        else:
-            common_features = set()
-
-        self.required_features = {
-            "always_required": common_features,
-            "per_part_required": per_part_features
-        }
-
     def get_tile_types(self):
         """ Return list of tile types """
         return self.tile_types.keys()
@@ -181,17 +168,9 @@ class Database(object):
         of fasm features.
         """
 
-        # No required features in the db, return empty list
-        if self.required_features is None:
+        # No required features in the db or part not given, return empty list
+        if self.required_features is None or part is None:
             return set()
 
-        # Get a list of required features for all parts
-        features = set()
-        if "always_required" in self.required_features:
-            features |= set(self.required_features["always_required"])
-
-        # Append list of part specific features
-        if part is not None:
-            features |= set(self.required_features["per_part_required"][part])
-
-        return features
+        # Return list of part specific features
+        return self.required_features[part]
diff --git a/utils/fasm2frames.py b/utils/fasm2frames.py
index f540fc7e..1efd2a4e 100755
--- a/utils/fasm2frames.py
+++ b/utils/fasm2frames.py
@@ -170,13 +170,19 @@ def main():
         db_root_kwargs['required'] = False
         db_root_kwargs['default'] = os.path.join(database_dir, database)
 
-    def_part = os.getenv("XRAY_PART")
+    db_part = os.getenv("XRAY_PART")
+    db_part_kwargs = {}
+    if db_part is None:
+        db_part_kwargs['required'] = True
+    else:
+        db_part_kwargs['required'] = False
+        db_part_kwargs['default'] = db_part
 
     parser.add_argument('--db-root', help="Database root.", **db_root_kwargs)
     parser.add_argument(
         '--part',
-        default=def_part,
-        help="Part name. When not given defaults to XRAY_PART env. var.")
+        help="Part name. When not given defaults to XRAY_PART env. var.",
+        **db_part_kwargs)
     parser.add_argument(
         '--sparse', action='store_true', help="Don't zero fill all frames")
     parser.add_argument(