diff --git a/cyclonedx_py/_internal/utils/pep621.py b/cyclonedx_py/_internal/utils/pep621.py
index a128dff9f..cfb3ac979 100644
--- a/cyclonedx_py/_internal/utils/pep621.py
+++ b/cyclonedx_py/_internal/utils/pep621.py
@@ -60,7 +60,7 @@ def project2licenses(project: dict[str, Any], lfac: 'LicenseFactory', *,
         # https://peps.python.org/pep-0621/#classifiers
         # https://packaging.python.org/en/latest/specifications/core-metadata/#classifier-multiple-use
         yield from classifiers2licenses(classifiers, lfac, lack)
-    if plicense := project.get('license'):
+    if isinstance(plicense := project.get('license'), dict):
         # https://packaging.python.org/en/latest/specifications/pyproject-toml/#license
         # https://peps.python.org/pep-0621/#license
         # https://packaging.python.org/en/latest/specifications/core-metadata/#license
@@ -87,6 +87,7 @@ def project2licenses(project: dict[str, Any], lfac: 'LicenseFactory', *,
                                          text=AttachedText(content=plicense_text))
             else:
                 yield license
+    # Silently skip any other types (including string/PEP 639)
 
 
 def project2extrefs(project: dict[str, Any]) -> Generator['ExternalReference', None, None]:
diff --git a/tests/integration/test_utils_pep621.py b/tests/integration/test_utils_pep621.py
new file mode 100644
index 000000000..463cddd48
--- /dev/null
+++ b/tests/integration/test_utils_pep621.py
@@ -0,0 +1,79 @@
+# This file is part of CycloneDX Python
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+# Copyright (c) OWASP Foundation. All Rights Reserved.
+
+from os.path import join
+from tempfile import TemporaryDirectory
+from unittest import TestCase
+
+from cyclonedx.factory.license import LicenseFactory
+from cyclonedx.model import Encoding
+from cyclonedx.model.license import DisjunctiveLicense, LicenseAcknowledgement
+from ddt import ddt, named_data
+
+from cyclonedx_py._internal.utils.pep621 import project2licenses
+
+
+@ddt()
+class TestUtilsPEP621(TestCase):
+
+    def test_project2licenses_license_dict_text(self) -> None:
+        project = {
+            'name': 'testpkg',
+            'license': {'text': 'This is the license text.'},
+        }
+        lfac = LicenseFactory()
+        with TemporaryDirectory() as tmpdir:
+            licenses = list(project2licenses(project, lfac, fpath=join(tmpdir, 'pyproject.toml')))
+        self.assertEqual(len(licenses), 1)
+        lic = licenses[0]
+        self.assertIsInstance(lic, DisjunctiveLicense)
+        self.assertIsNone(lic.id)
+        self.assertIsNone(lic.text.encoding)
+        self.assertEqual(lic.text.content, 'This is the license text.')
+        self.assertEqual(lic.acknowledgement, LicenseAcknowledgement.DECLARED)
+
+    def test_project2licenses_license_dict_file(self) -> None:
+        project = {
+            'name': 'testpkg',
+            'license': {'file': 'license.txt'},
+        }
+        lfac = LicenseFactory()
+        with TemporaryDirectory() as tmpdir:
+            with open(join(tmpdir, project['license']['file']), 'w') as tf:
+                tf.write('File license text')
+            licenses = list(project2licenses(project, lfac, fpath=join(tmpdir, 'pyproject.toml')))
+        self.assertEqual(len(licenses), 1)
+        lic = licenses[0]
+        self.assertIsInstance(lic, DisjunctiveLicense)
+        self.assertIs(lic.text.encoding, Encoding.BASE_64)
+        self.assertEqual(lic.text.content, 'RmlsZSBsaWNlbnNlIHRleHQ=')
+        self.assertEqual(lic.acknowledgement, LicenseAcknowledgement.DECLARED)
+
+    @named_data(
+        ('none', None),
+        ('string', 'MIT'),
+        ('list', ['MIT', 'Apache-2.0'])
+    )
+    def test_project2licenses_license_non_dict(self, license: any) -> None:
+        project = {
+            'name': 'testpkg',
+            'license': license,
+        }
+        lfac = LicenseFactory()
+        with TemporaryDirectory() as tmpdir:
+            licenses = list(project2licenses(project, lfac, fpath=join(tmpdir, 'pyproject.toml')))
+        self.assertEqual(len(licenses), 0)