diff --git a/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/Components.java b/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/Components.java
index a3d7ba04..229bd22b 100644
--- a/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/Components.java
+++ b/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/Components.java
@@ -31,6 +31,7 @@ import javax.swing.border.Border;
 import javax.swing.border.CompoundBorder;
 import javax.swing.event.DocumentEvent;
 import javax.swing.event.DocumentListener;
+import javax.swing.text.DefaultFormatterFactory;
 
 
 /**
@@ -310,6 +311,10 @@ public abstract class Components {
                 CompoundBorder editorBorder = BorderFactory.createCompoundBorder(
                         BorderFactory.createLineBorder( Res.colors().controlBorder(), 1, true ),
                         BorderFactory.createEmptyBorder( 4, 4, 4, 4 ) );
+                DefaultFormatterFactory formatterFactory = new DefaultFormatterFactory();
+                if (model instanceof UnsignedIntegerModel)
+                    formatterFactory.setDefaultFormatter( ((UnsignedIntegerModel)model).getFormatter() );
+                ((DefaultEditor) getEditor()).getTextField().setFormatterFactory( formatterFactory );
                 ((DefaultEditor) getEditor()).getTextField().setBorder( editorBorder );
                 setAlignmentX( LEFT_ALIGNMENT );
                 setBorder( null );
diff --git a/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/UnsignedIntegerModel.java b/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/UnsignedIntegerModel.java
index 02fa57fb..68e24dc4 100644
--- a/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/UnsignedIntegerModel.java
+++ b/platform-independent/java/gui/src/main/java/com/lyndir/masterpassword/gui/util/UnsignedIntegerModel.java
@@ -19,20 +19,18 @@
 package com.lyndir.masterpassword.gui.util;
 
 import com.google.common.primitives.UnsignedInteger;
+import java.text.ParseException;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
 import javax.swing.*;
-import javax.swing.event.ChangeEvent;
 import javax.swing.event.ChangeListener;
 
 
 /**
  * @author lhunath, 2016-10-29
  */
-public class UnsignedIntegerModel extends SpinnerNumberModel
-implements Selectable<UnsignedInteger, UnsignedIntegerModel> {
-
-    private static final long serialVersionUID = 1L;
+@SuppressWarnings("serial")
+public class UnsignedIntegerModel extends SpinnerNumberModel implements Selectable<UnsignedInteger, UnsignedIntegerModel> {
 
     @Nullable
     private ChangeListener changeListener;
@@ -64,6 +62,37 @@ implements Selectable<UnsignedInteger, UnsignedIntegerModel> {
         return (UnsignedInteger) super.getNumber();
     }
 
+    @Override
+    public UnsignedInteger getMinimum() {
+        return (UnsignedInteger) super.getMinimum();
+    }
+
+    @Override
+    public UnsignedInteger getMaximum() {
+        return (UnsignedInteger) super.getMaximum();
+    }
+
+    @Override
+    public UnsignedInteger getStepSize() {
+        return (UnsignedInteger) super.getStepSize();
+    }
+
+    @Override
+    public UnsignedInteger getNextValue() {
+        if ((getMaximum() == null) || (getMaximum().compareTo( getNumber() ) > 0))
+            return getNumber().plus( getStepSize() );
+
+        return getMaximum();
+    }
+
+    @Override
+    public UnsignedInteger getPreviousValue() {
+        if ((getMinimum() == null) || (getMinimum().compareTo( getNumber() ) < 0))
+            return getNumber().minus( getStepSize() );
+
+        return getMinimum();
+    }
+
     @Override
     public UnsignedIntegerModel selection(@Nullable final Consumer<UnsignedInteger> selectionConsumer) {
         if (changeListener != null) {
@@ -89,4 +118,22 @@ implements Selectable<UnsignedInteger, UnsignedIntegerModel> {
         setValue( selectedItem );
         return selection( selectionConsumer );
     }
+
+    public JFormattedTextField.AbstractFormatter getFormatter() {
+        return new JFormattedTextField.AbstractFormatter() {
+            @Override
+            @Nullable
+            public Object stringToValue(@Nullable final String text)
+                    throws ParseException {
+                return (text != null)? UnsignedInteger.valueOf( text ): null;
+            }
+
+            @Override
+            @Nullable
+            public String valueToString(final Object value)
+                    throws ParseException {
+                return (value != null)? value.toString(): null;
+            }
+        };
+    }
 }
diff --git a/platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPFileSite.java b/platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPFileSite.java
index 974f89fa..bb6200b1 100644
--- a/platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPFileSite.java
+++ b/platform-independent/java/model/src/main/java/com/lyndir/masterpassword/model/impl/MPFileSite.java
@@ -75,7 +75,9 @@ public class MPFileSite extends MPBasicSite<MPFileUser, MPFileQuestion> {
         return url;
     }
 
-    public void setUrl(@Nullable final String url) {
+    public void setUrl(@Nullable String url) {
+        if ((url != null) && url.isEmpty())
+            url = null;
         if (Objects.equals( this.url, url))
             return;