diff --git a/group.cpp b/group.cpp
index ec8f4a1c2b..784d64a98e 100644
--- a/group.cpp
+++ b/group.cpp
@@ -382,7 +382,7 @@ void Workspace::updateMinimizedOfTransients(AbstractClient* c)
 /*!
   Sets the client \a c's transient windows' on_all_desktops property to \a on_all_desktops.
  */
-void Workspace::updateOnAllDesktopsOfTransients(Client* c)
+void Workspace::updateOnAllDesktopsOfTransients(AbstractClient* c)
 {
     for (auto it = c->transients().constBegin();
             it != c->transients().constEnd();
diff --git a/workspace.h b/workspace.h
index 7b515bb863..89cccd6f70 100644
--- a/workspace.h
+++ b/workspace.h
@@ -263,7 +263,7 @@ public:
     }
 
     void updateMinimizedOfTransients(AbstractClient*);
-    void updateOnAllDesktopsOfTransients(Client*);
+    void updateOnAllDesktopsOfTransients(AbstractClient*);
     void checkTransients(xcb_window_t w);
 
     void storeSession(KConfig* config, SMSavePhase phase);