diff --git a/tests/integration/test_artifacts.py b/tests/integration/test_artifacts.py
index 147b940..462fdb6 100644
--- a/tests/integration/test_artifacts.py
+++ b/tests/integration/test_artifacts.py
@@ -6,6 +6,7 @@
 
 import os
 import shutil
+import threading
 from pathlib import Path
 
 import pygit2
@@ -226,3 +227,36 @@ def test_iter() -> None:
     assert pkgs[1].version == "v2.0.1"
     assert pkgs[2].name == "pck3"
     assert pkgs[2].version is None
+
+
+# pygit2 protects us against producing diverging histories anyway:
+#   _pygit2.GitError: failed to create commit: current tip is not the first
+#   parent
+# but the test is nice reassurance.
+def test_simultaneous_commit():
+    parallelism = 100
+    ad = new_test_artifacts()
+    artifacts: Artifacts = ad["artifacts"]
+    initial_commit_oid = ad["initial_commit_oid"]
+
+    new_tree, _ = add_test_file_to_repo(artifacts)
+
+    e = threading.Event()
+
+    def fn(i: int):
+        e.wait()
+        artifacts.commit_and_push(new_tree, f"I am thread {i}")
+
+    threads = [
+        threading.Thread(target=fn, args=[i]) for i in range(parallelism)
+    ]
+    for thread in threads:
+        thread.start()
+    e.set()
+    for thread in threads:
+        thread.join()
+
+    commit = artifacts.repo.head.peel(pygit2.Commit)
+    for _ in range(parallelism):
+        commit = commit.parents[0]
+    assert commit.oid == initial_commit_oid
diff --git a/tests/integration/test_environment.py b/tests/integration/test_environment.py
index df068f3..34153a2 100644
--- a/tests/integration/test_environment.py
+++ b/tests/integration/test_environment.py
@@ -15,6 +15,7 @@
 
 from softpack_core.artifacts import Artifacts, app
 from softpack_core.schemas.environment import (
+    BuilderError,
     CreateEnvironmentSuccess,
     DeleteEnvironmentSuccess,
     Environment,
@@ -26,7 +27,6 @@
     State,
     UpdateEnvironmentSuccess,
     WriteArtifactSuccess,
-    BuilderError,
 )
 from tests.integration.utils import file_in_remote
 
@@ -127,7 +127,9 @@ def test_create_path_invalid_disallowed(httpx_post, testable_env_input):
     assert isinstance(result, InvalidInputError)
 
 
-def test_create_cleans_up_after_builder_failure(httpx_post, testable_env_input):
+def test_create_cleans_up_after_builder_failure(
+    httpx_post, testable_env_input
+):
     httpx_post.side_effect = Exception('could not contact builder')
     result = Environment.create(testable_env_input)
     assert isinstance(result, BuilderError)