diff --git a/src/protocols/RTTY.cpp b/src/protocols/RTTY.cpp
index 7409e4ae..9427c87a 100644
--- a/src/protocols/RTTY.cpp
+++ b/src/protocols/RTTY.cpp
@@ -102,7 +102,7 @@ RTTYClient::RTTYClient(PhysicalLayer* phy) {
   _phy = phy;
 }
 
-int16_t RTTYClient::begin(float base, uint16_t shift, uint16_t rate, uint8_t encoding, uint8_t stopBits) {
+int16_t RTTYClient::begin(float base, uint32_t shift, uint16_t rate, uint8_t encoding, uint8_t stopBits) {
   // save configuration
   _encoding = encoding;
   _stopBits = stopBits;
@@ -125,7 +125,7 @@ int16_t RTTYClient::begin(float base, uint16_t shift, uint16_t rate, uint8_t enc
   _bitDuration = (uint32_t)1000000/rate;
 
   // calculate module carrier frequency resolution
-  uint16_t step = round((_phy->getCrystalFreq() * 1000000) / (uint32_t(1) << _phy->getDivExponent()));
+  uint32_t step = round((_phy->getCrystalFreq() * 1000000) / (uint32_t(1) << _phy->getDivExponent()));
 
   // check minimum shift value
   if(shift < step / 2) {
diff --git a/src/protocols/RTTY.h b/src/protocols/RTTY.h
index fd3f16e9..6a62cfb0 100644
--- a/src/protocols/RTTY.h
+++ b/src/protocols/RTTY.h
@@ -101,7 +101,7 @@ class RTTYClient {
 
       \returns \ref status_codes
     */
-    int16_t begin(float base, uint16_t shift, uint16_t rate, uint8_t encoding = ASCII, uint8_t stopBits = 1);
+    int16_t begin(float base, uint32_t shift, uint16_t rate, uint8_t encoding = ASCII, uint8_t stopBits = 1);
 
     /*!
       \brief Send out idle condition (RF tone at mark frequency).
@@ -142,7 +142,7 @@ class RTTYClient {
 
     uint8_t _encoding;
     uint32_t _base;
-    uint16_t _shift;
+    uint32_t _shift;
     uint16_t _bitDuration;
     uint8_t _dataBits;
     uint8_t _stopBits;