diff --git a/include/clipp.h b/include/clipp.h
index 06d45ee..d7b101e 100644
--- a/include/clipp.h
+++ b/include/clipp.h
@@ -1,7 +1,7 @@
 /*****************************************************************************
  *  ___  _    _   ___ ___
  * |  _|| |  | | | _ \ _ \   CLIPP - command line interfaces for modern C++
- * | |_ | |_ | | |  _/  _/   version 1.2.2
+ * | |_ | |_ | | |  _/  _/   version 1.2.3
  * |___||___||_| |_| |_|     https://github.com/muellan/clipp
  *
  * Licensed under the MIT License <http://opensource.org/licenses/MIT>.
@@ -4366,11 +4366,16 @@ struct select_values {
  *****************************************************************************/
 class match_t {
 public:
+    using size_type = arg_string::size_type;
+
     match_t() = default;
+
     match_t(arg_string s, scoped_dfs_traverser p):
         str_{std::move(s)}, pos_{std::move(p)}
     {}
 
+    size_type length() const noexcept { return str_.size(); }
+
     const arg_string& str() const noexcept { return str_; }
     const scoped_dfs_traverser& pos() const noexcept { return pos_; }
 
@@ -4420,28 +4425,30 @@ full_match(scoped_dfs_traverser pos, const arg_string& arg,
  *****************************************************************************/
 template<class ParamSelector>
 match_t
-prefix_match(scoped_dfs_traverser pos, const arg_string& arg,
-             const ParamSelector& select)
+longest_prefix_match(scoped_dfs_traverser pos, const arg_string& arg,
+                     const ParamSelector& select)
 {
+    match_t longest;
+
     while(pos) {
         if(pos->is_param()) {
             const auto& param = pos->as_param();
             if(select(param)) {
-                const auto match = param.match(arg);
+                auto match = param.match(arg);
                 if(match.prefix()) {
                     if(match.length() == arg.size()) {
                         return match_t{arg, std::move(pos)};
                     }
-                    else {
-                        return match_t{arg.substr(match.at(), match.length()),
-                                       std::move(pos)};
+                    else if(match.length() > longest.length()) {
+                        longest = match_t{arg.substr(match.at(), match.length()), 
+                                          pos};
                     }
                 }
             }
         }
         ++pos;
     }
-    return match_t{};
+    return longest;
 }
 
 
@@ -4747,7 +4754,7 @@ class parser
     bool try_match_joined_sequence(arg_string arg,
                                    const ParamSelector& acceptFirst)
     {
-        auto fstMatch = detail::prefix_match(pos_, arg, acceptFirst);
+        auto fstMatch = detail::longest_prefix_match(pos_, arg, acceptFirst);
 
         if(!fstMatch) return false;
 
@@ -4824,7 +4831,7 @@ class parser
         std::vector<match_t> matches;
 
         while(!arg.empty()) {
-            auto match = detail::prefix_match(parse.pos_, arg, select);
+            auto match = detail::longest_prefix_match(parse.pos_, arg, select);
 
             if(!match) return false;
 
diff --git a/test/prefix_test.cpp b/test/prefix_test.cpp
new file mode 100644
index 0000000..6282ce8
--- /dev/null
+++ b/test/prefix_test.cpp
@@ -0,0 +1,92 @@
+/*****************************************************************************
+ *
+ * CLIPP - command line interfaces for modern C++
+ *
+ * released under MIT license
+ *
+ * (c) 2017-2019 André Müller; foss@andremueller-online.de
+ *
+ *****************************************************************************/
+
+#include "testing.h"
+
+
+//-------------------------------------------------------------------
+struct active {
+    active() = default;
+    active(bool a_, int i_): a{a_}, i{i_} {}
+    bool a = false;
+    int i = 0;
+
+    friend bool operator == (const active& x, const active& y) noexcept {
+        return (x.a == y.a && x.i == y.i);
+    }
+};
+
+
+//-------------------------------------------------------------------
+static void
+test(int lineNo,
+     const std::initializer_list<const char*> args,
+     const active& matches )
+{
+    using namespace clipp;
+    active m;
+
+    auto cli = (
+        option("-a").set(m.a),
+        option("-ab", "-a-b", "-a-b=") & value("i", m.i)
+    );
+
+    run_wrapped_variants({ __FILE__, lineNo }, args, cli,
+              [&]{ m = active{}; },
+              [&]{ return m == matches; });
+}
+
+
+//-------------------------------------------------------------------
+int main()
+{
+    using std::string;
+
+    try {
+        test(__LINE__, {""},      active{0,0});
+        test(__LINE__, {"-a"},    active{1,0});
+
+        test(__LINE__, {"-ab"},   active{0,0});
+        test(__LINE__, {"-a-b"},  active{0,0});
+        test(__LINE__, {"-a-b="}, active{0,0});
+
+        test(__LINE__, {"-ab",   "2"}, active{0,2});
+        test(__LINE__, {"-a-b",  "3"}, active{0,3});
+        test(__LINE__, {"-a-b=", "4"}, active{0,4});
+
+        test(__LINE__, {"-ab2"  }, active{0,2});
+        test(__LINE__, {"-a-b3" }, active{0,3});
+        test(__LINE__, {"-a-b=4"}, active{0,4});
+
+        test(__LINE__, {"-a", "-ab",   "2"}, active{1,2});
+        test(__LINE__, {"-a", "-a-b",  "3"}, active{1,3});
+        test(__LINE__, {"-a", "-a-b=", "4"}, active{1,4});
+
+        test(__LINE__, {"-a", "-ab2"  }, active{1,2});
+        test(__LINE__, {"-a", "-a-b3" }, active{1,3});
+        test(__LINE__, {"-a", "-a-b=4"}, active{1,4});
+
+        test(__LINE__, {"-ab",   "2", "-a"}, active{1,2});
+        test(__LINE__, {"-a-b",  "3", "-a"}, active{1,3});
+        test(__LINE__, {"-a-b=", "4", "-a"}, active{1,4});
+
+        test(__LINE__, {"-a", "-ab"  }, active{1,0});
+        test(__LINE__, {"-a", "-a-b" }, active{1,0});
+        test(__LINE__, {"-a", "-a-b="}, active{1,0});
+
+        test(__LINE__, {"-ab",   "-a"}, active{1,0});
+        test(__LINE__, {"-a-b",  "-a"}, active{1,0});
+        test(__LINE__, {"-a-b=", "-a"}, active{1,0});
+    }
+    catch(std::exception& e) {
+        std::cerr << e.what() << std::endl;
+        return 1;
+    }
+}