diff --git a/Mage.Client/src/main/java/mage/client/MageFrame.java b/Mage.Client/src/main/java/mage/client/MageFrame.java
index 95fa08395a3..ce3b5205b00 100644
--- a/Mage.Client/src/main/java/mage/client/MageFrame.java
+++ b/Mage.Client/src/main/java/mage/client/MageFrame.java
@@ -896,6 +896,13 @@ public class MageFrame extends javax.swing.JFrame implements MageClient {
     }//GEN-LAST:event_btnConnectActionPerformed
 
     public void btnAboutActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_btnAboutActionPerformed
+        JInternalFrame[] windows = desktopPane.getAllFramesInLayer(JLayeredPane.POPUP_LAYER);
+        for (JInternalFrame window : windows) {
+            if (window instanceof AboutDialog) {
+                // don't open the window twice.
+                return;
+            }
+        }
         AboutDialog aboutDialog = new AboutDialog();
         desktopPane.add(aboutDialog, JLayeredPane.POPUP_LAYER);
         aboutDialog.showDialog(version);
diff --git a/Mage.Client/src/main/java/mage/client/dialog/AboutDialog.java b/Mage.Client/src/main/java/mage/client/dialog/AboutDialog.java
index 84a0869526e..6298ea6f27f 100644
--- a/Mage.Client/src/main/java/mage/client/dialog/AboutDialog.java
+++ b/Mage.Client/src/main/java/mage/client/dialog/AboutDialog.java
@@ -48,7 +48,7 @@ public class AboutDialog extends MageDialog {
     public AboutDialog() {
         this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
         initComponents();
-        // this.modal = false;
+        this.modal = true;
     }
 
     public void showDialog(MageVersion version) {