diff --git a/swash/processing/swash.py b/swash/processing/swash.py
index fc5aa71..0fc4756 100644
--- a/swash/processing/swash.py
+++ b/swash/processing/swash.py
@@ -1,4 +1,5 @@
 import logging
+import os
 import sys
 import argparse
 import pathlib
@@ -30,7 +31,9 @@ with tempfile.TemporaryDirectory(prefix="swash_", dir=".") as tmp_raw:
 
     log.info(f"Copying files to '{tmpdir}'")
     shutil.copy2(inp, tmpdir)
-    shutil.copytree(pathlib.Path(config.get("data", "out")), tmpdir, dirs_exist_ok=True)
+    shutil.copytree(
+        pathlib.Path(config.get("data", "out")), tmpdir, dirs_exist_ok=True
+    )
 
     if config.has_option("swash", "mpi"):
         mpi = ("-mpi", config.get("swash", "mpi"))
@@ -46,7 +49,11 @@ with tempfile.TemporaryDirectory(prefix="swash_", dir=".") as tmp_raw:
         log.info(f"Running {cmd}")
 
         swash_run = subprocess.Popen(
-            cmd, cwd=tmpdir, stdout=logfile, stderr=logfile, env={"PATH": path}
+            cmd,
+            cwd=tmpdir,
+            stdout=logfile,
+            stderr=logfile,
+            env={"PATH": f"{path}:{os.environ['PATH']}"},
         )
 
         code = swash_run.wait()