diff --git a/src/pybind/ceph_argparse.py b/src/pybind/ceph_argparse.py
index 7ec7b8b2f0c..1f6e90b6c1d 100644
--- a/src/pybind/ceph_argparse.py
+++ b/src/pybind/ceph_argparse.py
@@ -843,6 +843,11 @@ def validate(args, signature, partial=False):
                     # wanted n, got too few
                     if partial:
                         return d
+                    # special-case the "0 expected 1" case
+                    if desc.numseen == 0 and desc.n == 1:
+                        raise ArgumentNumber(
+                            'missing required parameter {0}'.format(desc)
+                        )
                     raise ArgumentNumber(
                         'saw {0} of {1}, expected {2}'.\
                         format(desc.numseen, desc, desc.n)
@@ -951,6 +956,7 @@ def validate_command(sigdict, args, verbose=False):
                     # Stop now, because we have the right command but
                     # some other input is invalid
                     print >> sys.stderr, "Invalid command: ", str(e)
+                    print >> sys.stderr, concise_sig(sig), ': ', cmd['help']
                     return {}
             if found:
                 break