diff --git a/dep_freshness/tests/test_versions.py b/dep_freshness/tests/test_versions.py
index d988267..3c73a4e 100644
--- a/dep_freshness/tests/test_versions.py
+++ b/dep_freshness/tests/test_versions.py
@@ -45,12 +45,19 @@ def test_newest_stable_ignores_unparseable_entries():
     # PyPI stub packages date-stamp a fourth component. Capping the regex at
     # three reported this exact pin as unpinned *against its own value*.
     ("==2.33.0.20260712", "2.33.0.20260712"),
+    # PEP 440 post/dev/pre releases are exact pins too (pytest-asyncio).
+    ("1.4.1.post1", "1.4.1.post1"), ("==1.4.1.post1", "1.4.1.post1"),
+    ("2.0.post3", "2.0.post3"), ("1.0.dev2", "1.0.dev2"),
+    ("==2.0rc1", "2.0rc1"), ("1.2.3a1", "1.2.3a1"), ("1.2b4", "1.2b4"),
+    ("1.0.post1.dev2", "1.0.post1.dev2"),
 ])
 def test_exact_pins_are_recognised(raw, expected):
     assert exact_pin(raw) == expected
 
 
-@pytest.mark.parametrize("raw", ["^1.6.0", ">=1.6.0", "any", "*", "", ">=1,<2", "~1.2"])
+@pytest.mark.parametrize("raw", ["^1.6.0", ">=1.6.0", "any", "*", "", ">=1,<2", "~1.2",
+    ">=1.4.1.post1", "~=1.4", "1.4.post", "1.4.postx", "1.4.1.post1,<2",
+])
 def test_ranges_are_not_exact_pins(raw):
     assert exact_pin(raw) is None
 
@@ -61,6 +68,13 @@ def test_behind_compares_versions():
     assert not behind("1.8.0", "1.7.0")
 
 
+def test_a_post_release_is_newer_than_its_base_release():
+    assert behind("1.4.1", "1.4.1.post1")
+    assert not behind("1.4.1.post1", "1.4.1")
+    assert not is_prerelease("1.4.1.post1")
+    assert newest_stable(["1.4.1", "1.4.1.post1", "1.4.0"]) == "1.4.1.post1"
+
+
 def test_behind_never_fires_on_unparseable_input():
     """An unpinned constraint is UNPINNED, never dressed up as staleness."""
     assert not behind("^1.6.0", "1.7.0")
diff --git a/dep_freshness/versions.py b/dep_freshness/versions.py
index 3d19abe..5fa79a2 100644
--- a/dep_freshness/versions.py
+++ b/dep_freshness/versions.py
@@ -160,10 +160,12 @@ def behind(pinned: str, latest: str) -> bool:
 # date-stamp a fourth (`types-requests==2.33.0.20260712`), and capping at
 # three reported an exact pin as unpinned against itself. A project-name
 # prefix (`natural-comparator-1.1`) is part of the pin, since it is what the
-# registry's version list spells.
+# registry's version list spells. PEP 440 `(a|b|rc)N`, `.postN` and `.devN`
+# follow the release (`pytest-asyncio==1.4.1.post1`), before the semver suffix.
 EXACT = re.compile(
     r"^\s*(?:==\s*)?(?:[A-Za-z][A-Za-z_.-]*?-(?=v?\d))?"
-    r"v?\d+(?:\.\d+)*(?:[-+][0-9A-Za-z.-]+)?\s*$"
+    r"v?\d+(?:\.\d+)*(?:(?:a|b|rc)\d+)?(?:\.post\d+)?(?:\.dev\d+)?"
+    r"(?:[-+][0-9A-Za-z.-]+)?\s*$"
 )