Lister form has an owner.

Wlx2Explorer/Forms/MainForm.cs

@@ -214,7 +214,8 @@ private void ShowListerForm()
             }
             else
             {
-                _listerForm.Show();
+                var foregroundWindowHandle = NativeMethods.GetForegroundWindow();
+                _listerForm.Show(new Win32WindowWrapper(foregroundWindowHandle));
                 _listerForm.Activate();
             }
         }

Wlx2Explorer/Win32WindowWrapper.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Windows.Forms;
+
+namespace Wlx2Explorer
+{
+    class Win32WindowWrapper : IWin32Window
+    {
+        public IntPtr Handle { get; private set; }
+
+        public Win32WindowWrapper(IntPtr handle)
+        {
+            Handle = handle;
+        }
+    }
+}

Wlx2Explorer/Wlx2Explorer.csproj

@@ -104,6 +104,7 @@
     </Compile>
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Win32WindowWrapper.cs" />
     <EmbeddedResource Include="Forms\AboutForm.resx">
       <DependentUpon>AboutForm.cs</DependentUpon>
     </EmbeddedResource>