diff --git a/placement.cpp b/placement.cpp
index 46cb9d446c..722e782d38 100644
--- a/placement.cpp
+++ b/placement.cpp
@@ -361,7 +361,7 @@ void Placement::reinitCascading(int desktop)
     }
 }
 
-QPoint Workspace::cascadeOffset(const Client *c) const
+QPoint Workspace::cascadeOffset(const AbstractClient *c) const
 {
     QRect area = clientArea(PlacementArea, c->geometry().center(), c->desktop());
     return QPoint(area.width()/48, area.height()/48);
diff --git a/workspace.h b/workspace.h
index 900e06a722..db369e2681 100644
--- a/workspace.h
+++ b/workspace.h
@@ -218,7 +218,7 @@ public:
     void stackScreenEdgesUnderOverrideRedirect();
 
 public:
-    QPoint cascadeOffset(const Client *c) const;
+    QPoint cascadeOffset(const AbstractClient *c) const;
 
 private:
     Compositor *m_compositor;