diff --git a/sprockets_postgres.py b/sprockets_postgres.py
index 02c895d..27a7cd3 100644
--- a/sprockets_postgres.py
+++ b/sprockets_postgres.py
@@ -110,7 +110,7 @@ class PostgresConnector:
     """
     def __init__(self,
                  cursor: aiopg.Cursor,
-                 on_error: typing.Callable,
+                 on_error: typing.Optional[typing.Callable] = None,
                  on_duration: typing.Optional[typing.Callable] = None,
                  timeout: Timeout = None):
         self.cursor = cursor
@@ -246,9 +246,10 @@ class PostgresConnector:
         try:
             await method(**kwargs)
         except (asyncio.TimeoutError, psycopg2.Error) as err:
-            exc = self._on_error(metric_name, err)
-            if exc:
-                raise exc
+            if self._on_error:
+                err = self._on_error(metric_name, err)
+            if err:
+                raise err
         else:
             results = await self._query_results()
             if self._on_duration:
@@ -313,7 +314,8 @@ class ApplicationMixin:
 
     @contextlib.asynccontextmanager
     async def postgres_connector(self,
-                                 on_error: typing.Callable,
+                                 on_error: typing.Optional[
+                                     typing.Callable] = None,
                                  on_duration: typing.Optional[
                                      typing.Callable] = None,
                                  timeout: Timeout = None,