diff --git a/setup.py b/setup.py
index f7e563a26..75bfc0be2 100644
--- a/setup.py
+++ b/setup.py
@@ -18,12 +18,12 @@
 def get_proj_version(proj_dir: Path) -> str:
     proj_version = os.environ.get("PROJ_VERSION")
     if proj_version:
-        return parse_version(proj_version).base_version
+        return proj_version
     proj = proj_dir / "bin" / "proj"
     proj_ver = subprocess.check_output(str(proj), stderr=subprocess.STDOUT).decode(
         "ascii"
     )
-    return parse_version((proj_ver.split()[1]).strip(",")).base_version
+    return (proj_ver.split()[1]).strip(",")
 
 
 def check_proj_version(proj_version: str) -> None:
@@ -155,7 +155,9 @@ def get_extension_modules():
 
     proj_version = get_proj_version(proj_dir)
     check_proj_version(proj_version)
-    proj_version_major, proj_version_minor, proj_version_patch = proj_version.split(".")
+    proj_version_major, proj_version_minor, proj_version_patch = parse_version(
+        proj_version
+    ).base_version.split(".")
 
     # setup extension options
     ext_options = {