diff --git a/prymer/offtarget/bwa.py b/prymer/offtarget/bwa.py
index d84e7a8..7052e74 100644
--- a/prymer/offtarget/bwa.py
+++ b/prymer/offtarget/bwa.py
@@ -45,6 +45,7 @@
 """  # noqa: E501
 
 import os
+import subprocess
 from dataclasses import dataclass
 from pathlib import Path
 from typing import ClassVar
diff --git a/prymer/util/executable_runner.py b/prymer/util/executable_runner.py
index e69500c..e2612ba 100644
--- a/prymer/util/executable_runner.py
+++ b/prymer/util/executable_runner.py
@@ -42,7 +42,7 @@ def __init__(
         command: list[str],
         stdin: int = subprocess.PIPE,
         stdout: int = subprocess.PIPE,
-        stderr: int = subprocess.PIPE,
+        stderr: int = subprocess.DEVNULL,
     ) -> None:
         if len(command) == 0:
             raise ValueError(f"Invocation must not be empty, received {command}")