diff --git a/NIDAQmxInterface.cpp b/NIDAQmxInterface.cpp
index 23ad797..adc1469 100644
--- a/NIDAQmxInterface.cpp
+++ b/NIDAQmxInterface.cpp
@@ -223,9 +223,9 @@ void NIDAQmxInterface::DAQmxSetDO(uInt8 qry_port_bit, bool arm_timer, bool isSet
     if (daq->do_port != 0)
     {
         if(isSet){
-            daq->do_bit_wrt |= 1 << qry_port_bit-1;
+            daq->do_bit_wrt |= (1 << (qry_port_bit-1));
         }else{
-            daq->do_bit_wrt &= ~(1 << qry_port_bit-1);
+            daq->do_bit_wrt &= ~(1 << (qry_port_bit-1));
         }
         DAQmxErrChk(DAQmxWriteDigitalU8(daq->do_port, 1, 1, 10.0, DAQmx_Val_GroupByChannel, &daq->do_bit_wrt, &written, NULL));
     }