diff --git a/changelog.d/+built-sdist-import-check.infrastructure.md b/changelog.d/+built-sdist-import-check.infrastructure.md
new file mode 100644
index 00000000..ba7469b9
--- /dev/null
+++ b/changelog.d/+built-sdist-import-check.infrastructure.md
@@ -0,0 +1 @@
+Add a build-time smoke test that installs the freshly built source distribution and imports the public API shims.
diff --git a/noxfile.py b/noxfile.py
index 4458bf30..fedc60dd 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -178,6 +178,7 @@ def cover(session):
 @nox.session(python=PYTHON_DEFAULT_VERSION)
 def build(session):
     """Build the distribution."""
+    session.run('rm', '-rf', 'build', 'dist', external=True)
     session.run('uv', 'build', external=True)
 
     # Set outputs for GitHub Actions
@@ -190,6 +191,32 @@ def build(session):
             version = os.environ['GITHUB_REF'].replace('refs/tags/v', '')
             print(f'version={version}', file=github_output)
 
+    sdists = sorted(pathlib.Path('dist').glob('b2sdk-*.tar.gz'))
+    if len(sdists) != 1:
+        session.error(f'Expected exactly one source distribution, found {len(sdists)}: {sdists!r}')
+
+    session.install(str(sdists[0]))
+    session.cd('dist')  # avoid importing from the checkout instead of the built package
+    session.run(
+        'python',
+        '-c',
+        (
+            'import pathlib; '
+            'from b2sdk import v0, v1, v2, v3; '
+            'repo_root = pathlib.Path.cwd().parent.resolve(); '
+            'source_root = repo_root / "b2sdk"; '
+            "module_files = {'v0': pathlib.Path(v0.__file__).resolve(), "
+            "'v1': pathlib.Path(v1.__file__).resolve(), "
+            "'v2': pathlib.Path(v2.__file__).resolve(), "
+            "'v3': pathlib.Path(v3.__file__).resolve()}; "
+            'print(module_files); '
+            "assert all(not path.is_relative_to(source_root) for path in module_files.values()), "
+            "f'Imported modules from checkout: {module_files!r}'; "
+            "assert all('site-packages' in path.parts for path in module_files.values()), "
+            "f'Imported modules from an unexpected location: {module_files!r}'"
+        ),
+    )
+
 
 @nox.session(python=PYTHON_DEFAULT_VERSION)
 def doc(session):