diff --git a/sqlite_minutils/db.py b/sqlite_minutils/db.py
index 5e739ca..16f0ed8 100644
--- a/sqlite_minutils/db.py
+++ b/sqlite_minutils/db.py
@@ -413,7 +413,7 @@ def query(
         :param params: Parameters to use in that query - an iterable for ``where id = ?``
           parameters, or a dictionary for ``where id = :id``
         """
-        cursor = self.execute(sql, tuple(params or tuple()))
+        cursor = self.execute(sql, params or tuple())
         keys = [d[0] for d in cursor.description]
         for row in cursor:
             yield dict(zip(keys, row))
@@ -431,7 +431,9 @@ def execute(
         if self._tracer:
             self._tracer(sql, parameters)
         if parameters is not None:
-            return self.conn.execute(sql, tuple(parameters))
+            if not isinstance(parameters, dict):
+                parameters = tuple(parameters)
+            return self.conn.execute(sql, parameters)
         else:
             return self.conn.execute(sql)