diff --git a/src/modules/SX128x/SX128x.cpp b/src/modules/SX128x/SX128x.cpp
index 7a719ab4..8a07a2d4 100644
--- a/src/modules/SX128x/SX128x.cpp
+++ b/src/modules/SX128x/SX128x.cpp
@@ -996,8 +996,14 @@ int16_t SX128x::setSyncWord(const uint8_t* syncWord, uint8_t len) {
     this->syncWordLen = len;
   }
 
+  uint16_t syncAddr = len == 5 ? RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_4 :
+                      len == 4 ? RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_3 :
+                      len == 3 ? RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_2 :
+                      len == 2 ? RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_1 :
+                                 RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_0;
+
   // update sync word
-  int16_t state = SX128x::writeRegister(RADIOLIB_SX128X_REG_SYNC_WORD_1_BYTE_4, const_cast<uint8_t*>(syncWord), len);
+  int16_t state = SX128x::writeRegister(syncAddr, const_cast<uint8_t*>(syncWord), len);
   RADIOLIB_ASSERT(state);
 
   // update packet parameters