diff --git a/lib/optparse.rb b/lib/optparse.rb
index ade98708d6..11218fe940 100644
--- a/lib/optparse.rb
+++ b/lib/optparse.rb
@@ -1503,7 +1503,7 @@ XXX
         else
           raise ArgumentError, "argument pattern given twice"
         end
-        o.each {|pat, *v| pattern[pat] = v.fetch(0) {pat}}
+        o.each {|pat, *v| pattern[pat.to_s] = v.fetch(0) {pat}}
       when Module
         raise ArgumentError, "unsupported argument type: #{o}", ParseError.filter_backtrace(caller(4))
       when *ArgumentStyle.keys
diff --git a/test/optparse/test_placearg.rb b/test/optparse/test_placearg.rb
index c6dc7abcf9..511541fecd 100644
--- a/test/optparse/test_placearg.rb
+++ b/test/optparse/test_placearg.rb
@@ -8,6 +8,7 @@ class TestOptionParserPlaceArg < TestOptionParser
     @opt.def_option("--option [VAL]") {|x| @flag = x}
     @opt.def_option("-T [level]", /^[0-4]$/, Integer) {|x| @topt = x}
     @opt.def_option("--enum [VAL]", [:Alpha, :Bravo, :Charlie]) {|x| @enum = x}
+    @opt.def_option("--integer [VAL]", [1, 2, 3]) {|x| @integer = x}
     @topt = nil
     @opt.def_option("-n") {}
     @opt.def_option("--regexp [REGEXP]", Regexp) {|x| @reopt = x}
@@ -99,4 +100,9 @@ class TestOptionParserPlaceArg < TestOptionParser
     assert_equal([], no_error {@opt.parse!(%w"--enum=A")})
     assert_equal(:Alpha, @enum)
   end
+
+  def test_enum_conversion
+    assert_equal([], no_error {@opt.parse!(%w"--integer=1")})
+    assert_equal(1, @integer)
+  end
 end