diff --git a/docs/release-notes/version-4.4.17.rst b/docs/release-notes/version-4.4.17.rst
index c5f8155e..a0760939 100644
--- a/docs/release-notes/version-4.4.17.rst
+++ b/docs/release-notes/version-4.4.17.rst
@@ -9,3 +9,10 @@ Version 4.4.17 of mod_wsgi can be obtained from:
 For details on the availability of Windows binaries see:
 
   https://github.com/GrahamDumpleton/mod_wsgi/tree/master/win32
+
+Bugs Fixed
+----------
+
+1. If ``mod_wsgi-express`` was run under a user ID for which there was no
+password entry in the system password file, it would fail when looking up
+the user name. If this occurs now use ``#nnn`` as the default user name.
diff --git a/src/server/__init__.py b/src/server/__init__.py
index 4b925891..fbc77c7c 100644
--- a/src/server/__init__.py
+++ b/src/server/__init__.py
@@ -50,7 +50,10 @@ def where():
     return MOD_WSGI_SO
 
 def default_run_user():
-    return pwd.getpwuid(os.getuid()).pw_name
+    try:
+        return pwd.getpwuid(os.getuid()).pw_name
+    except KeyError:
+        return '#%d' % os.getuid()
 
 def default_run_group():
     try: