diff --git a/pyproject.toml b/pyproject.toml
index a1fb8fe..6f5a61f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=64", "setuptools-scm"]
+requires = ["setuptools>=77.0.3", "setuptools-scm"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -7,7 +7,8 @@ name = "apiprober"
 version = "0.1.0"
 description = "Passive API discovery and documentation CLI for undocumented REST services"
 readme = "README.md"
-license = {text = "MIT"}
+license = "MIT"
+license-files = ["LICENSE"]
 requires-python = ">=3.8"
 authors = [
     {name = "Lukas Geiger", email = "lukisch@users.noreply.github.com"},
@@ -16,7 +17,6 @@ keywords = ["api", "api-discovery", "rest-api", "openapi", "documentation", "pas
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
diff --git a/test_smoke.py b/test_smoke.py
index e3ca15b..1e9bd7e 100644
--- a/test_smoke.py
+++ b/test_smoke.py
@@ -534,6 +534,19 @@ def test_readme_exists(self):
         assert "ApiProber" in content or "API Prober" in content
 
 
+class TestPackagingMetadata:
+    """Regressionstest für den PEP-639-Lizenzvertrag."""
+
+    def test_license_metadata_uses_spdx_and_includes_license_file(self):
+        """MIT bleibt explizit, maschinenlesbar und im Paket enthalten."""
+        pyproject = (API_PROBER_DIR / "pyproject.toml").read_text(encoding="utf-8")
+
+        assert 'requires = ["setuptools>=77.0.3", "setuptools-scm"]' in pyproject
+        assert 'license = "MIT"' in pyproject
+        assert 'license-files = ["LICENSE"]' in pyproject
+        assert "License ::" not in pyproject
+
+
 # ============================================================================
 #  MAIN (für direktes Ausführen)
 # ============================================================================