diff --git a/cwltool/provenance.py b/cwltool/provenance.py
index 7c7e38cfd..498ef57ff 100644
--- a/cwltool/provenance.py
+++ b/cwltool/provenance.py
@@ -79,9 +79,12 @@
 def _whoami() -> Tuple[str, str]:
     """Return the current operating system account as (username, fullname)."""
     username = getuser()
+    fullname = ""
     try:
         fullname = pwd.getpwuid(os.getuid())[4].split(",")[0]
     except (KeyError, IndexError):
+        pass
+    if fullname == "":
         fullname = username
 
     return (username, fullname)