diff --git a/action_setup_python_poetry/invalid_package_versions.py b/action_setup_python_poetry/invalid_package_versions.py
index d43393c..b5615c9 100644
--- a/action_setup_python_poetry/invalid_package_versions.py
+++ b/action_setup_python_poetry/invalid_package_versions.py
@@ -20,7 +20,7 @@ def get_invalid_package_versions(pyproject_toml_file_text: str) -> Sequence[tupl
         (package, version_str)
         for package, version in (
             *poetry_data["dependencies"].items(),
-            *poetry_data["dev-dependencies"].items(),
+            *poetry_data.get("dev-dependencies", {}).items(),
             *itertools.chain.from_iterable(
                 (group["dependencies"].items() for _, group in poetry_data.get("group", {}).items()),
             ),
diff --git a/action_setup_python_poetry/tests/data/pyproject_mock_no_dev_dependencies.toml b/action_setup_python_poetry/tests/data/pyproject_mock_no_dev_dependencies.toml
new file mode 100644
index 0000000..4af3ddd
--- /dev/null
+++ b/action_setup_python_poetry/tests/data/pyproject_mock_no_dev_dependencies.toml
@@ -0,0 +1,21 @@
+[tool.poetry]
+name = "test-project"
+version = "0.1.0"
+description = "Testing only"
+authors = ["moneymeets GmbH <service@moneymeets.com>"]
+
+[tool.poetry.scripts]
+merge_checks_runner = 'invalid_package_versions.runner:run'
+
+[tool.poetry.dependencies]
+python = "~3.12"
+
+[tool.poetry.group.test-group-1.dependencies]
+test-package-1 = "*"
+
+[tool.poetry.group.test-group-2.dependencies]
+test-package-2 = "*"
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"
diff --git a/action_setup_python_poetry/tests/test_get_invalid_package_versions.py b/action_setup_python_poetry/tests/test_get_invalid_package_versions.py
index d100341..6d79b36 100644
--- a/action_setup_python_poetry/tests/test_get_invalid_package_versions.py
+++ b/action_setup_python_poetry/tests/test_get_invalid_package_versions.py
@@ -7,13 +7,12 @@
 
 
 class GetInvalidPackageVersionsTest(TestCase):
-    valid_pyproject_toml = (TEST_DATA_DIR / "pyproject_mock_valid.toml").read_text()
-    invalid_pyproject_toml = (TEST_DATA_DIR / "pyproject_mock_invalid.toml").read_text()
-
     def test_get_invalid_package_versions_success(self):
-        self.assertEqual((), get_invalid_package_versions(self.valid_pyproject_toml))
+        valid_pyproject_toml = (TEST_DATA_DIR / "pyproject_mock_valid.toml").read_text()
+        self.assertEqual((), get_invalid_package_versions(valid_pyproject_toml))
 
     def test_get_invalid_package_versions_failed(self):
+        invalid_pyproject_toml = (TEST_DATA_DIR / "pyproject_mock_invalid.toml").read_text()
         self.assertEqual(
             (
                 ("python", ">=3.12"),
@@ -21,5 +20,9 @@ def test_get_invalid_package_versions_failed(self):
                 ("test-package-1", ">=1"),
                 ("test-package-2", ">=1"),
             ),
-            get_invalid_package_versions(self.invalid_pyproject_toml),
+            get_invalid_package_versions(invalid_pyproject_toml),
         )
+
+    def test_no_dev_dependencies(self):
+        no_dev_dependencies_pyproject_toml = (TEST_DATA_DIR / "pyproject_mock_no_dev_dependencies.toml").read_text()
+        self.assertEqual((), get_invalid_package_versions(no_dev_dependencies_pyproject_toml))