diff --git a/tabbox.cpp b/tabbox.cpp
index 828fc85616..19cd92c525 100644
--- a/tabbox.cpp
+++ b/tabbox.cpp
@@ -1149,6 +1149,8 @@ int Workspace::previousDesktopFocusChain( int iDesktop ) const
 */
 Client* Workspace::nextFocusChainClient( Client* c ) const
     {
+    if ( !c )
+        return 0;
     int desktop = c->isOnAllDesktops() ? currentDesktop() : c->desktop();
     if ( focus_chain[desktop].isEmpty() )
         return 0;
@@ -1167,6 +1169,8 @@ Client* Workspace::nextFocusChainClient( Client* c ) const
 */
 Client* Workspace::previousFocusChainClient( Client* c ) const
     {
+    if ( !c )
+        return 0;
     int desktop = c->isOnAllDesktops() ? currentDesktop() : c->desktop();
     if ( focus_chain[desktop].isEmpty() )
         return 0;