diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index 4ed4892..33851e1 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -678,7 +678,8 @@ inline OptionNames split_option_names(const std::string &text)
         "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
         "abcdefghijklmnopqrstuvwxyz"
         "0123456789"
-        "_-";
+        "_-.?";
+
       if (!std::isalnum(text[token_start_pos], std::locale::classic()) ||
           text.find_first_not_of(option_name_valid_chars, token_start_pos) < next_delimiter_pos) {
         throw_or_mimic<exceptions::invalid_option_format>(text);
@@ -752,9 +753,9 @@ std::basic_regex<char> falsy_pattern
   ("(f|F)(alse)?|0");
 
 std::basic_regex<char> option_matcher
-  ("--([[:alnum:]][-_[:alnum:]]+)(=(.*))?|-([[:alnum:]].*)");
+  ("--([[:alnum:]][-_[:alnum:]\\.]+)(=(.*))?|-([[:alnum:]].*)");
 std::basic_regex<char> option_specifier
-  ("([[:alnum:]][-_[:alnum:]]*)(,[ ]*[[:alnum:]][-_[:alnum:]]*)*");
+  ("([[:alnum:]][-_[:alnum:]\\.]*)(,[ ]*[[:alnum:]][-_[:alnum:]]*)*");
 std::basic_regex<char> option_specifier_separator(", *");
 
 } // namespace
diff --git a/test/options.cpp b/test/options.cpp
index 6da106e..288810d 100644
--- a/test/options.cpp
+++ b/test/options.cpp
@@ -56,6 +56,7 @@ TEST_CASE("Basic options", "[options]")
     ("a,av", "a short option with a value", cxxopts::value<std::string>())
     ("6,six", "a short number option")
     ("p, space", "an option with space between short and long")
+    ("period.delimited", "an option with a period in the long name")
     ("nothing", "won't exist", cxxopts::value<std::string>())
     ;
 
@@ -77,7 +78,8 @@ TEST_CASE("Basic options", "[options]")
     "-z",
     "--over",
     "--dog",
-    "--lazy"
+    "--lazy",
+    "--period.delimited",
   });
 
   auto** actual_argv = argv.argv();
@@ -97,9 +99,10 @@ TEST_CASE("Basic options", "[options]")
   CHECK(result.count("quick") == 2);
   CHECK(result.count("f") == 2);
   CHECK(result.count("z") == 4);
+  CHECK(result.count("period.delimited") == 1);
 
   auto& arguments = result.arguments();
-  REQUIRE(arguments.size() == 15);
+  REQUIRE(arguments.size() == 16);
   CHECK(arguments[0].key() == "long");
   CHECK(arguments[0].value() == "true");
   CHECK(arguments[0].as<bool>() == true);