diff --git a/src/protocols/RTTY/RTTY.cpp b/src/protocols/RTTY/RTTY.cpp
index 640a79a8..0d0552bf 100644
--- a/src/protocols/RTTY/RTTY.cpp
+++ b/src/protocols/RTTY/RTTY.cpp
@@ -195,7 +195,7 @@ size_t RTTYClient::write(uint8_t* buff, size_t len) {
 size_t RTTYClient::write(uint8_t b) {
   space();
 
-  for(uint16_t mask = 0x01; mask <= (uint16_t)(0x01 << (_dataBits - 1)); mask <<= 1) {
+  for(uint16_t mask = 0x01; mask <= (uint16_t)(0x01 << (uint16_t)(_dataBits - 1)); mask <<= 1) {
     if(b & mask) {
       mark();
     } else {