diff --git a/Lib/optparse.py b/Lib/optparse.py
--- a/Lib/optparse.py
+++ b/Lib/optparse.py
@@ -147,8 +147,9 @@ class AmbiguousOptionError (BadOptionErr
         self.possibilities = possibilities
 
     def __str__(self):
-        return (_("ambiguous option: %s (%s?)")
-                % (self.opt_str, ", ".join(self.possibilities)))
+        return (_("ambiguous option: %(option)s (%(possibilities)s?)")
+                % {"option": self.opt_str,
+                   "possibilities": ", ".join(self.possibilities)})
 
 
 class HelpFormatter:
@@ -425,7 +426,8 @@ def check_builtin(option, opt, value):
         return cvt(value)
     except ValueError:
         raise OptionValueError(
-            _("option %s: invalid %s value: %r") % (opt, what, value))
+            _("option %(option)s: invalid %(type)s value: %(value)r")
+            % {"option": opt, "type": what, "value": value})
 
 def check_choice(option, opt, value):
     if value in option.choices:
@@ -433,8 +435,8 @@ def check_choice(option, opt, value):
     else:
         choices = ", ".join(map(repr, option.choices))
         raise OptionValueError(
-            _("option %s: invalid choice: %r (choose from %s)")
-            % (opt, value, choices))
+            _("option %(option)s: invalid choice: %(value)r (choose from %(choices)s)")
+            % {"option": opt, "value": value, "choices": choices})
 
 # Not supplying a default is different from a default of None,
 # so we need an explicit "not supplied" value.