diff --git a/src/NeoSWSerial.cpp b/src/NeoSWSerial.cpp
index ce8edfe..5cf7d81 100644
--- a/src/NeoSWSerial.cpp
+++ b/src/NeoSWSerial.cpp
@@ -539,6 +539,9 @@ size_t NeoSWSerial::write(uint8_t txChar)
     //    the last 0 data bit.  Then we could wait for the
     //    remaining 1 data bits and stop bit with interrupts 
     //    re-enabled.
+    
+  txBitMask = digitalPinToBitMask( txPin );
+  txPort    = portOutputRegister( digitalPinToPort( txPin ) );
 
     while (txBit++ < 9) {   // repeat for start bit + 8 data bits
       if (b)      // if bit is set