diff --git a/src/modules/SX127x/SX127x.cpp b/src/modules/SX127x/SX127x.cpp
index e842cdd0..fe22a1e7 100644
--- a/src/modules/SX127x/SX127x.cpp
+++ b/src/modules/SX127x/SX127x.cpp
@@ -599,9 +599,10 @@ int16_t SX127x::setPreambleLength(uint16_t preambleLength) {
     return(state);
 
   } else if(modem == SX127X_FSK_OOK) {
-    // set preamble length
-    state = _mod->SPIsetRegValue(SX127X_REG_PREAMBLE_MSB_FSK, (uint8_t)((preambleLength >> 8) & 0xFF));
-    state |= _mod->SPIsetRegValue(SX127X_REG_PREAMBLE_LSB_FSK, (uint8_t)(preambleLength & 0xFF));
+    // set preamble length (in bytes)
+    uint16_t numBytes = preambleLength / 8;
+    state = _mod->SPIsetRegValue(SX127X_REG_PREAMBLE_MSB_FSK, (uint8_t)((numBytes >> 8) & 0xFF));
+    state |= _mod->SPIsetRegValue(SX127X_REG_PREAMBLE_LSB_FSK, (uint8_t)(numBytes & 0xFF));
     return(state);
   }
 
diff --git a/src/modules/SX127x/SX127x.h b/src/modules/SX127x/SX127x.h
index a42605e1..98906354 100644
--- a/src/modules/SX127x/SX127x.h
+++ b/src/modules/SX127x/SX127x.h
@@ -745,9 +745,9 @@ class SX127x: public PhysicalLayer {
     int16_t setCurrentLimit(uint8_t currentLimit);
 
     /*!
-      \brief Sets %LoRa preamble length. Allowed values range from 6 to 65535. Only available in %LoRa mode.
+      \brief Sets %LoRa or FSK preamble length. Allowed values range from 6 to 65535 in %LoRa mode or 0 to 65535 in FSK mode.
 
-      \param preambleLength Preamble length to be set (in symbols).
+      \param preambleLength Preamble length to be set (in symbols when in LoRa mode or bits in FSK mode).
 
       \returns \ref status_codes
     */