diff --git a/ur_rtde_driver/src/ros/hardware_interface.cpp b/ur_rtde_driver/src/ros/hardware_interface.cpp
index 3928b10..6e7db61 100644
--- a/ur_rtde_driver/src/ros/hardware_interface.cpp
+++ b/ur_rtde_driver/src/ros/hardware_interface.cpp
@@ -576,6 +576,7 @@ bool HardwareInterface::setIO(ur_msgs::SetIORequest& req, ur_msgs::SetIOResponse
   }
   else
   {
+    LOG_ERROR("Cannot execute function %u. This is not (yet) supported.", req.fun);
     res.success = false;
   }