diff --git a/Configuration.cpp b/Configuration.cpp
index 2bb5fc8..d63fe6f 100644
--- a/Configuration.cpp
+++ b/Configuration.cpp
@@ -1017,7 +1017,7 @@ Configuration::impl::impl (Configuration * self, QDir const& temp_directory,
   // validation
   //
   ui_->callsign_line_edit->setValidator (new CallsignValidator {this});
-  ui_->grid_line_edit->setValidator (new MaidenheadLocatorValidator {this});
+  ui_->grid_line_edit->setValidator (new MaidenheadLocatorValidator {this, MaidenheadLocatorValidator::Length::doubleextended});
   ui_->add_macro_line_edit->setValidator (new QRegExpValidator {message_alphabet, this});
   ui_->station_message_line_edit->setValidator (new QRegExpValidator {message_alphabet, this});
   ui_->qth_message_line_edit->setValidator (new QRegExpValidator {message_alphabet, this});
diff --git a/Configuration.ui b/Configuration.ui
index d32ed20..85bc029 100644
--- a/Configuration.ui
+++ b/Configuration.ui
@@ -80,7 +80,7 @@
                  <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;4-digit Maidenhead Locator&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
                 </property>
                 <property name="maxLength">
-                 <number>4</number>
+                 <number>16</number>
                 </property>
                </widget>
               </item>
diff --git a/MaidenheadLocatorValidator.hpp b/MaidenheadLocatorValidator.hpp
index 25c2664..29a1a9a 100644
--- a/MaidenheadLocatorValidator.hpp
+++ b/MaidenheadLocatorValidator.hpp
@@ -11,7 +11,7 @@ class MaidenheadLocatorValidator final
   : public QValidator
 {
 public:
-  enum class Length {field = 2, square = 4, subsquare = 6, extended = 8};
+  enum class Length {field = 2, square = 4, subsquare = 6, extended = 8, doubleextended = 16};
   MaidenheadLocatorValidator (QObject * parent = nullptr
                               , Length length = Length::subsquare
                               , Length required = Length::square);