diff --git a/server_http.hpp b/server_http.hpp
index 0e9b965..6041767 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -165,7 +165,7 @@ namespace SimpleWeb {
             CaseInsensitiveMultimap parse_query_string() {
                 auto pos = path.find('?');
                 if (pos != std::string::npos && pos + 1 < path.size())
-                    return SimpleWeb::parse_query_string(path.substr(pos + 1));
+                    return SimpleWeb::QueryString::parse(path.substr(pos + 1));
                 else
                     return CaseInsensitiveMultimap();
             }
diff --git a/tests/parse_test.cpp b/tests/parse_test.cpp
index ddff80e..a5bbda7 100644
--- a/tests/parse_test.cpp
+++ b/tests/parse_test.cpp
@@ -122,8 +122,18 @@ int main() {
     auto percent_decoded="testing æøå !#$&'()*+,/:;=?@[]";
     auto percent_encoded="testing+æøå+%21%23%24%26%27%28%29%2A%2B%2C%2F%3A%3B%3D%3F%40%5B%5D";
     assert(Percent::encode(percent_decoded)==percent_encoded);
+    assert(Percent::decode(percent_encoded)==percent_decoded);
     assert(Percent::decode(Percent::encode(percent_decoded))==percent_decoded);
     
+    SimpleWeb::CaseInsensitiveMultimap fields={{"test1", "æøå"}, {"test2", "!#$&'()*+,/:;=?@[]"}};
+    auto query_string1="test1=æøå&test2=%21%23%24%26%27%28%29%2A%2B%2C%2F%3A%3B%3D%3F%40%5B%5D";
+    auto query_string2="test2=%21%23%24%26%27%28%29%2A%2B%2C%2F%3A%3B%3D%3F%40%5B%5D&test1=æøå";
+    auto query_string_result=QueryString::create(fields);
+    assert(query_string_result==query_string1 || query_string_result==query_string2);
+    auto fields_result1=QueryString::parse(query_string1);
+    auto fields_result2=QueryString::parse(query_string2);
+    assert(fields_result1==fields_result2 && fields_result1==fields);
+    
     ServerTest serverTest;
     serverTest.io_service=std::make_shared<asio::io_service>();
     
diff --git a/utility.hpp b/utility.hpp
index e0605a2..a5cc8f0 100644
--- a/utility.hpp
+++ b/utility.hpp
@@ -59,7 +59,7 @@ public:
     for(auto &chr : value) {
       if(chr == ' ')
         result += '+';
-      else if(chr == '!' || chr == '#' || chr == '$' || (chr >= '&' && chr <= ',') || (chr >= '/' && chr <= ';') || chr == '=' || chr=='?' || chr == '@' || chr == '[' || chr == ']')
+      else if(chr == '!' || chr == '#' || chr == '$' || (chr >= '&' && chr <= ',') || (chr >= '/' && chr <= ';') || chr == '=' || chr == '?' || chr == '@' || chr == '[' || chr == ']')
         result += std::string("%") + hex_chars[chr >> 4] + hex_chars[chr & 15];
       else
         result += chr;
@@ -70,7 +70,7 @@ public:
 
   static std::string decode(const std::string &value) {
     std::string result;
-    result.reserve((value.size() + 2) / 3); // minimum size of result
+    result.reserve(value.size() / 3 + (value.size() % 3)); // minimum size of result
 
     for(size_t i = 0; i < value.size(); ++i) {
       auto &chr = value[i];
@@ -90,41 +90,61 @@ public:
   }
 };
 
-/// Returns query keys with percent-decoded values.
-inline CaseInsensitiveMultimap parse_query_string(const std::string &query_string) {
-  CaseInsensitiveMultimap result;
+class QueryString {
+public:
+  static std::string create(const CaseInsensitiveMultimap &fields) {
+    std::string result;
+
+    bool first = true;
+    for(auto &field : fields) {
+      result += (!first ? "&" : "") + field.first + '=' + Percent::encode(field.second);
+      first = false;
+    }
 
-  if(query_string.empty())
     return result;
+  }
 
-  size_t parameter_pos = 0;
-  size_t parameter_end_pos = -1;
-  size_t value_pos = -1;
-  for(size_t c = 0; c < query_string.size(); ++c) {
-    if(query_string[c] == '&') {
-      auto parameter = query_string.substr(parameter_pos, (parameter_end_pos == std::string::npos ? c : parameter_end_pos) - parameter_pos);
-      if(!parameter.empty()) {
-        auto value = value_pos == std::string::npos ? std::string() : query_string.substr(value_pos, c - value_pos);
-        result.emplace(std::move(parameter), Percent::decode(value));
+  /// Returns query keys with percent-decoded values.
+  static CaseInsensitiveMultimap parse(const std::string &query_string) {
+    CaseInsensitiveMultimap result;
+
+    if(query_string.empty())
+      return result;
+
+    size_t name_pos = 0;
+    size_t name_end_pos = -1;
+    size_t value_pos = -1;
+    for(size_t c = 0; c < query_string.size(); ++c) {
+      if(query_string[c] == '&') {
+        auto name = query_string.substr(name_pos, (name_end_pos == std::string::npos ? c : name_end_pos) - name_pos);
+        if(!name.empty()) {
+          auto value = value_pos == std::string::npos ? std::string() : query_string.substr(value_pos, c - value_pos);
+          result.emplace(std::move(name), Percent::decode(value));
+        }
+        name_pos = c + 1;
+        name_end_pos = -1;
+        value_pos = -1;
+      }
+      else if(query_string[c] == '=') {
+        name_end_pos = c;
+        value_pos = c + 1;
       }
-      parameter_pos = c + 1;
-      parameter_end_pos = -1;
-      value_pos = -1;
     }
-    else if(query_string[c] == '=') {
-      parameter_end_pos = c;
-      value_pos = c + 1;
+    if(name_pos < query_string.size()) {
+      auto name = query_string.substr(name_pos, name_end_pos - name_pos);
+      if(!name.empty()) {
+        auto value = value_pos >= query_string.size() ? std::string() : query_string.substr(value_pos);
+        result.emplace(std::move(name), Percent::decode(value));
+      }
     }
-  }
-  if(parameter_pos < query_string.size()) {
-    auto parameter = query_string.substr(parameter_pos, parameter_end_pos - parameter_pos);
-    if(!parameter.empty()) {
-      auto value = value_pos >= query_string.size() ? std::string() : query_string.substr(value_pos);
-      result.emplace(std::move(parameter), Percent::decode(value));
-    }
-  }
 
-  return result;
+    return result;
+  }
+};
+
+/// Returns query keys with percent-decoded values.
+DEPRECATED inline CaseInsensitiveMultimap parse_query_string(const std::string &query_string) {
+  return QueryString::parse(query_string);
 }
 } // namespace SimpleWeb