diff --git a/tests/test_formats.py b/tests/test_formats.py
index 42a354c7..25c27f28 100755
--- a/tests/test_formats.py
+++ b/tests/test_formats.py
@@ -292,6 +292,13 @@ def test_build_dict_conforming_to_schema(self):
     # Test construction of a few metadata formats using
     # build_dict_conforming_to_schema().
 
+    # Try the wrong type of schema object.
+    STRING_SCHEMA = securesystemslib.schema.AnyString()
+
+    with self.assertRaises(ValueError):
+      tuf.formats.build_dict_conforming_to_schema(
+          STRING_SCHEMA, string='some string')
+
     # Try building Timestamp metadata.
     spec_version = tuf.SPECIFICATION_VERSION
     version = 8
diff --git a/tuf/formats.py b/tuf/formats.py
index 9846fa4f..2c5128db 100755
--- a/tuf/formats.py
+++ b/tuf/formats.py
@@ -516,9 +516,9 @@ def build_dict_conforming_to_schema(schema, **kwargs):
   """
 
   # Check the schema argument type (must provide check_match and _required).
-  if not isinstance(schema, SCHEMA.Schema):
+  if not isinstance(schema, SCHEMA.Object):
     raise ValueError(
-        'The first argument must be a schema.Schema object, but is not. '
+        'The first argument must be a schema.Object instance, but is not. '
         'Given schema: ' + repr(schema))
 
   # Make a copy of the provided fields so that the caller's provided values