diff --git a/install-pdm.py b/install-pdm.py
index 3107702914..3c1a8be3cd 100644
--- a/install-pdm.py
+++ b/install-pdm.py
@@ -202,7 +202,7 @@ def _get_latest_version(self) -> str:
         metadata = json.load(resp)
 
         def version_okay(v: str) -> bool:
-            return self.prerelease or all(p.isdigit() for p in v.split("."))
+            return self.prerelease or re.fullmatch(r"^(\d+)\.(\d+)\.(\d+)(\.(post\d+))?", v)
 
         def sort_version(v: str) -> tuple:
             parts = []
diff --git a/install-pdm.py.sha256 b/install-pdm.py.sha256
index a67ad8130c..1ad1db58f0 100644
--- a/install-pdm.py.sha256
+++ b/install-pdm.py.sha256
@@ -1 +1 @@
-07dacbddc508f70bc21347598b9764bc07440ebface340bdd1e96f7af9ea4267  install-pdm.py
+cd45cd6313c1cd0375d8b98b4adbc4f58b490c8e5c1e5b41b5b94d07e85d91e0  install-pdm.py