diff --git a/workspace.cpp b/workspace.cpp
index 50338ba6c8..3dd3d47517 100644
--- a/workspace.cpp
+++ b/workspace.cpp
@@ -54,6 +54,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #endif
 #include "atoms.h"
 #include "cursor.h"
+#include "killwindow.h"
 #include "placement.h"
 #include "notifications.h"
 #include "outline.h"
diff --git a/workspace.h b/workspace.h
index 42a555c8f9..a5dea6091e 100644
--- a/workspace.h
+++ b/workspace.h
@@ -37,7 +37,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "kdecoration.h"
 #include "sm.h"
-#include "killwindow.h"
 
 #include <X11/Xlib.h>
 
@@ -56,6 +55,7 @@ namespace KWin
 {
 
 class Client;
+class KillWindow;
 class Outline;
 class RootInfo;
 class Rules;