diff --git a/boxtree/cost.py b/boxtree/cost.py
index 2c451d33..835aa365 100644
--- a/boxtree/cost.py
+++ b/boxtree/cost.py
@@ -62,7 +62,6 @@
 """
 
 from abc import ABC, abstractmethod
-from collections.abc import Mapping
 from functools import partial
 from typing import TYPE_CHECKING, ClassVar
 
@@ -79,6 +78,7 @@
 if TYPE_CHECKING:
     from collections.abc import Mapping
 
+
 Template = partial(Template, strict_undefined=True)
 
 
diff --git a/boxtree/fmm.py b/boxtree/fmm.py
index 2800d249..0d88eaba 100644
--- a/boxtree/fmm.py
+++ b/boxtree/fmm.py
@@ -35,9 +35,6 @@
 
 from pytools import ProcessLogger
 
-from boxtree.traversal import FMMTraversalInfo
-from boxtree.tree import Tree
-
 
 if TYPE_CHECKING:
     from arraycontext import ArrayContext
@@ -45,6 +42,7 @@
     from boxtree.traversal import FMMTraversalInfo
     from boxtree.tree import Tree
 
+
 logger = logging.getLogger(__name__)