diff --git a/src/tox_gh_actions/plugin.py b/src/tox_gh_actions/plugin.py
index 65693d8..1fcbc9a 100644
--- a/src/tox_gh_actions/plugin.py
+++ b/src/tox_gh_actions/plugin.py
@@ -164,24 +164,27 @@ def get_python_version_keys() -> List[str]:
 
     Examples:
     - CPython 3.8.z => [3.8, 3]
-    - PyPy 3.6 (v7.3.z) => [pypy-3.6, pypy-3, pypy3]
+    - PyPy 3.6 (v7.3.z) => [pypy-3.6, pypy-3]
     - Pyston based on Python CPython 3.8.8 (v2.2) => [pyston-3.8, pyston-3]
+    - CPython 3.13.z (free-threading build) => [3.13t, 3.13, 3]
     """
-    major_version = str(sys.version_info[0])
-    major_minor_version = ".".join([str(i) for i in sys.version_info[:2]])
+    major, minor = sys.version_info[:2]
     if "PyPy" in sys.version:
         return [
-            "pypy-" + major_minor_version,
-            "pypy-" + major_version,
+            f"pypy-{major}.{minor}",
+            f"pypy-{major}",
         ]
     elif hasattr(sys, "pyston_version_info"):  # Pyston
         return [
-            "pyston-" + major_minor_version,
-            "pyston-" + major_version,
+            f"pyston-{major}.{minor}",
+            f"pyston-{major}",
         ]
     else:
         # Assume this is running on CPython
-        return [major_minor_version, major_version]
+        ret = [f"{major}.{minor}", f"{major}"]
+        if sys.abiflags:
+            ret.insert(0, f"{major}.{minor}{sys.abiflags}")
+        return ret
 
 
 def is_running_on_actions() -> bool:
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index d841d6a..0c276fd 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -247,29 +247,40 @@ def test_get_envlist_from_factors(
 
 
 @pytest.mark.parametrize(
-    "version,info,expected",
+    "version,info,abiflags,expected",
     [
         (
             "3.8.1 (default, Jan 22 2020, 06:38:00) \n[GCC 9.2.0]",
             (3, 8, 1, "final", 0),
+            "",
             ["3.8", "3"],
         ),
         (
             "3.6.9 (1608da62bfc7, Dec 23 2019, 10:50:04)\n"
             "[PyPy 7.3.0 with GCC 7.3.1 20180303 (Red Hat 7.3.1-5)]",
             (3, 6, 9, "final", 0),
+            "",
             ["pypy-3.6", "pypy-3"],
         ),
+        (
+            "3.13.0 experimental free-threading build (main, Oct 16 2024, 03:26:14) "
+            "[Clang 18.1.8 ]\n",
+            (3, 13, 0, "final", 0),
+            "t",
+            ["3.13t", "3.13", "3"],
+        ),
     ],
 )
 def test_get_version_keys(
     mocker: MockerFixture,
     version: str,
     info: Tuple[int, int, int, str, int],
+    abiflags: str,
     expected: List[str],
 ) -> None:
     mocker.patch("tox_gh_actions.plugin.sys.version", version)
     mocker.patch("tox_gh_actions.plugin.sys.version_info", info)
+    mocker.patch("tox_gh_actions.plugin.sys.abiflags", abiflags)
     assert plugin.get_python_version_keys() == expected