diff --git a/setuptools/version.py b/setuptools/version.py
index 75b2a14959..ec253c4144 100644
--- a/setuptools/version.py
+++ b/setuptools/version.py
@@ -1,6 +1,6 @@
 from ._importlib import metadata
 
 try:
-    __version__ = metadata.version('setuptools')
+    __version__ = metadata.version('setuptools') or '0.dev0+unknown'
 except Exception:
-    __version__ = 'unknown'
+    __version__ = '0.dev0+unknown'