diff --git a/src/com/t_oster/liblasercut/drivers/Lasersaur.java b/src/com/t_oster/liblasercut/drivers/Lasersaur.java
index de7752033d020ef303d2875bf1d2825f23847690..fd6bcf111613657496a170542e59b94d81e50824 100644
--- a/src/com/t_oster/liblasercut/drivers/Lasersaur.java
+++ b/src/com/t_oster/liblasercut/drivers/Lasersaur.java
@@ -379,6 +379,10 @@ public class Lasersaur extends LaserCutter {
     {
       throw new Exception("Error: Could not Open COM-Port '"+this.getComPort()+"'");
     }
+    if (!(tmp instanceof SerialPort))
+    {
+      throw new Exception("Port '"+this.getComPort()+"' is not a serial port.");
+    }
     SerialPort port = (SerialPort) tmp;
     port.setFlowControlMode(SerialPort.FLOWCONTROL_NONE);
     port.setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);