diff --git a/docs/api_reference.md b/docs/api_reference.md
index 3a2f5db8..de4f9f4a 100644
--- a/docs/api_reference.md
+++ b/docs/api_reference.md
@@ -274,7 +274,7 @@ CaseType = Union[Callable, Type, ModuleRef]
 
 A decorator for test functions or fixtures, to parametrize them based on test cases. It works similarly to [`@pytest.mark.parametrize`](https://docs.pytest.org/en/stable/parametrize.html): argnames represent a coma-separated string of arguments to inject in the decorated test function or fixture. The argument values (`argvalues` in [`@pytest.mark.parametrize`](https://docs.pytest.org/en/stable/parametrize.html)) are collected from the various case functions found according to `cases`, and injected as lazy values so that the case functions are called just before the test or fixture is executed.
 
-By default (`cases=AUTO`) the list of test cases is automatically drawn from the python module file named `test_<name>_cases.py` or if not found, `cases_<name>.py`,  where `test_<name>` is the current module name.
+By default (`cases=AUTO`) the list of test cases is automatically drawn from the python module file named `test_<name>_cases.py` or if not found, `cases_<name>.py`,  where `test_<name>` is the current module name. Also works for `tests.py` (`tests_cases.py`).
 
 Finally, the `cases` argument also accepts an explicit case function, cases-containing class, module or module name; or a list containing any mix of these elements. Note that both absolute and relative module names are supported.
 
diff --git a/docs/changelog.md b/docs/changelog.md
index 269fd663..7d58b24b 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -1,5 +1,10 @@
 # Changelog
 
+
+### 3.8.7 (in progress)
+
+- Allow `tests.py` to find tests from `tests_cases.py`.
+
 ### 3.8.6 - compatibility fix
 
 - Fixed issue with legacy python 2.7 and 3.5. Fixes [#352](https://github.com/smarie/python-pytest-cases/issues/352).
diff --git a/src/pytest_cases/case_parametrizer_new.py b/src/pytest_cases/case_parametrizer_new.py
index 9796f062..47c0f17e 100644
--- a/src/pytest_cases/case_parametrizer_new.py
+++ b/src/pytest_cases/case_parametrizer_new.py
@@ -304,7 +304,7 @@ def get_all_cases(parametrization_target=None,  # type: Callable
                 # as we don't know what to look for. We complain here
                 # rather than raising AssertionError in the call to
                 # import_default_cases_module. See #309.
-                if not caller_module_name.split('.')[-1].startswith('test_'):
+                if not _has_test_prefix(caller_module_name.split('.')[-1]):
                     raise ValueError(
                         'Cannot use `cases=AUTO` in file "%s". `cases=AUTO` is '
                         'only allowed in files whose name starts with "test_" '
@@ -324,6 +324,11 @@ def get_all_cases(parametrization_target=None,  # type: Callable
             if matches_tag_query(c, has_tag=has_tag, filter=filters)]
 
 
+def _has_test_prefix(module_name):  # type: (str) -> bool
+    prefixes = ('test_', 'tests')
+    return any(module_name.startswith(p) for p in prefixes)
+
+
 def get_parametrize_args(host_class_or_module,    # type: Union[Type, ModuleType]
                          cases_funs,              # type: List[Callable]
                          prefix,                  # type: str
@@ -693,7 +698,7 @@ def import_default_cases_module(test_module_name):
     except ModuleNotFoundError:
         # Then try `cases_<name>.py`
         parts = test_module_name.split('.')
-        assert parts[-1][0:5] == 'test_'
+        assert _has_test_prefix(parts[-1])
         cases_module_name2 = "%s.cases_%s" % ('.'.join(parts[:-1]), parts[-1][5:])
         try:
             cases_module = import_module(cases_module_name2)
diff --git a/tests/cases/issues/issue_309/tests.py b/tests/cases/issues/issue_309/tests.py
new file mode 100644
index 00000000..1d3e8b4b
--- /dev/null
+++ b/tests/cases/issues/issue_309/tests.py
@@ -0,0 +1,10 @@
+from pytest_cases import get_all_cases
+from pytest_cases.common_others import AUTO
+
+
+def mock_parameterization_target():
+    """A callable to use as parametrization target."""
+
+
+def test_get_all_cases_auto_works_in_tests_py():
+    get_all_cases(mock_parameterization_target, cases=AUTO)
diff --git a/tests/cases/issues/issue_309/tests_cases.py b/tests/cases/issues/issue_309/tests_cases.py
new file mode 100644
index 00000000..ce5818d7
--- /dev/null
+++ b/tests/cases/issues/issue_309/tests_cases.py
@@ -0,0 +1,2 @@
+def case_one():
+    return 1