diff --git a/assemblers/org.osbuild.oci-archive b/assemblers/org.osbuild.oci-archive
index bcd23daa..82ebb7af 100755
--- a/assemblers/org.osbuild.oci-archive
+++ b/assemblers/org.osbuild.oci-archive
@@ -103,7 +103,7 @@ MEDIA_TYPES = {
 
 def sha256sum(path: str) -> str:
     ret = subprocess.run(["sha256sum", path],
-                         capture_output=True,
+                         stdout=subprocess.PIPE,
                          encoding="utf-8",
                          check=True)
 
diff --git a/test/mod/test_util_ostree.py b/test/mod/test_util_ostree.py
index 381ce377..4d39b90f 100644
--- a/test/mod/test_util_ostree.py
+++ b/test/mod/test_util_ostree.py
@@ -78,7 +78,7 @@ class TestObjectStore(unittest.TestCase):
                      "tree",
                      "--print-only",
                      path],
-                    capture_output=True)
+                    stdout=subprocess.PIPE)
             self.assertEqual(r.returncode, 0)
             js = json.loads(r.stdout)
 
diff --git a/test/test.py b/test/test.py
index 032c53c8..69ee4710 100644
--- a/test/test.py
+++ b/test/test.py
@@ -176,7 +176,7 @@ class TestBase(unittest.TestCase):
         try:
             r = subprocess.run(["rpm-ostree", "--version"],
                                encoding="utf-8",
-                               capture_output=True,
+                               stdout=subprocess.PIPE,
                                check=False)
         except FileNotFoundError:
             return False