diff -r 44f455e6163d Lib/argparse.py
--- a/Lib/argparse.py	Thu Jun 27 12:23:29 2013 +0200
+++ b/Lib/argparse.py	Tue Jul 01 22:53:00 2014 -0700
@@ -1903,6 +1903,11 @@
             selected_pattern = arg_strings_pattern[start_index:]
             arg_counts = match_partial(positionals, selected_pattern)
 
+            if 'O' in selected_pattern: # better issue 15112 test
+                while arg_counts and arg_counts[-1] == 0:
+                    arg_counts.pop()
+
+
             # slice off the appropriate arg strings for each Positional
             # and add the Positional and its args to the list
             for action, arg_count in zip(positionals, arg_counts):
@@ -2188,8 +2193,9 @@
             nargs_pattern = '(-*A[A-]*)'
 
         # allow any number of options or arguments
+        # an optional pattern that starts with an A
         elif nargs == REMAINDER:
-            nargs_pattern = '([-AO]*)'
+            nargs_pattern = '(-*(?:A[-AO]*)?)'
 
         # allow one argument followed by any number of options or arguments
         elif nargs == PARSER:
diff -r 44f455e6163d Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py	Thu Jun 27 12:23:29 2013 +0200
+++ b/Lib/test/test_argparse.py	Tue Jul 01 22:53:00 2014 -0700
@@ -1252,6 +1252,7 @@
         ('-z Z X', NS(x='X', y=[], z='Z')),
         ('X A B -z Z', NS(x='X', y=['A', 'B', '-z', 'Z'], z=None)),
         ('X Y --foo', NS(x='X', y=['Y', '--foo'], z=None)),
+        ('X -z Z A B', NS(x='X', y=['A', 'B'], z='Z')),
     ]