Index: lib/optparse.rb
===================================================================
--- lib/optparse.rb	(revision 42822)
+++ lib/optparse.rb	(working copy)
@@ -1637,8 +1637,9 @@ XXX
   decimal = '\d+(?:_\d+)*'
   binary = 'b[01]+(?:_[01]+)*'
   hex = 'x[\da-f]+(?:_[\da-f]+)*'
-  octal = "0(?:[0-7]*(?:_[0-7]+)*|#{binary}|#{hex})"
+  octal = "0(?:[0-7]+(?:_[0-7]+)*|#{binary}|#{hex})?"
   integer = "#{octal}|#{decimal}"
+
   accept(Integer, %r"\A[-+]?(?:#{integer})"io) {|s,| Integer(s) if s}
 
   #
@@ -1664,22 +1665,34 @@ XXX
   #
   # Decimal integer format, to be converted to Integer.
   #
-  DecimalInteger = /\A[-+]?#{decimal}/io
-  accept(DecimalInteger) {|s,| s.to_i if s}
+  DecimalInteger = /\A([-+]?#{decimal})/io
+  accept(DecimalInteger, DecimalInteger) {|s,d|
+    begin
+      Integer(d)
+    rescue ArgumentError
+      raise OptionParser::InvalidArgument, s
+    end
+  }
 
   #
   # Ruby/C like octal/hexadecimal/binary integer format, to be converted to
   # Integer.
   #
   OctalInteger = /\A[-+]?(?:[0-7]+(?:_[0-7]+)*|0(?:#{binary}|#{hex}))/io
-  accept(OctalInteger) {|s,| s.oct if s}
+  accept(OctalInteger, OctalInteger) {|s,| s.oct if s}
 
   #
   # Decimal integer/float number format, to be converted to Integer for
   # integer format, Float for float format.
   #
   DecimalNumeric = floatpat     # decimal integer is allowed as float also.
-  accept(DecimalNumeric) {|s,| eval(s) if s}
+  accept(DecimalNumeric, floatpat) {|s,|
+    begin
+      eval(s)
+    rescue SyntaxError
+      raise OptionParser::InvalidArgument, s
+    end if s
+  }
 
   #
   # Boolean switch, which means whether it is present or not, whether it is