diff --git a/core.windows/src/org/netbeans/core/windows/WindowManagerImpl.java b/core.windows/src/org/netbeans/core/windows/WindowManagerImpl.java
--- a/core.windows/src/org/netbeans/core/windows/WindowManagerImpl.java
+++ b/core.windows/src/org/netbeans/core/windows/WindowManagerImpl.java
@@ -771,8 +771,8 @@ public final class WindowManagerImpl ext
     }
     
     /** Attaches TopComponent to one side of mode, it removes it from original one. */
-    public void attachTopComponentToSide(TopComponent tc, ModeImpl attachMode, String side) {
-        central.attachTopComponentsToSide(new TopComponent[] {tc}, attachMode, side);
+    public void attachTopComponentToSide(TopComponent tc, Mode attachMode, String side) {
+        central.attachTopComponentsToSide(new TopComponent[] {tc}, (ModeImpl)attachMode, side);
     }
     
     // XXX
diff --git a/openide.windows/src/org/openide/windows/DummyWindowManager.java b/openide.windows/src/org/openide/windows/DummyWindowManager.java
--- a/openide.windows/src/org/openide/windows/DummyWindowManager.java
+++ b/openide.windows/src/org/openide/windows/DummyWindowManager.java
@@ -709,4 +709,9 @@ final class DummyWindowManager extends W
             return active.get();
         }
     }
+
+    @Override
+    public void attachTopComponentToSide(TopComponent tc, Mode attachMode, String side) {
+        throw new UnsupportedOperationException("Not supported yet.");
+    }
 }
diff --git a/openide.windows/src/org/openide/windows/WindowManager.java b/openide.windows/src/org/openide/windows/WindowManager.java
--- a/openide.windows/src/org/openide/windows/WindowManager.java
+++ b/openide.windows/src/org/openide/windows/WindowManager.java
@@ -218,6 +218,9 @@ public abstract class WindowManager exte
     @Deprecated
     public abstract Workspace getCurrentWorkspace();
 
+    /** Attaches TopComponent to one side of mode, it removes it from original one. */
+    public abstract void attachTopComponentToSide(TopComponent tc, Mode attachMode, String side);
+    
     /** Finds <code>TopComponentGroup</code> of given name.
      * @return instance of TopComponetnGroup or null
      * @since 4.13 */