diff --git a/Lib/argparse.py b/Lib/argparse.py
index a300828..d29f161 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -404,13 +404,19 @@
                             inserts[start] += ' ['
                         else:
                             inserts[start] = '['
-                        inserts[end] = ']'
+                        if end in inserts:
+                            inserts[end] += ']'
+                        else:
+                            inserts[end] = ']'
                     else:
                         if start in inserts:
                             inserts[start] += ' ('
                         else:
                             inserts[start] = '('
-                        inserts[end] = ')'
+                        if end in inserts:
+                            inserts[end] += ')'
+                        else:
+                            inserts[end] = ')'
                     for i in range(start + 1, end):
                         inserts[i] = '|'