diff --git a/RFM69.cpp b/RFM69.cpp
index ed4d8b9..c94e383 100644
--- a/RFM69.cpp
+++ b/RFM69.cpp
@@ -438,7 +438,8 @@ void RFM69::encrypt(const char* key) {
   _haveEncryptKey = key;
 #endif
   setMode(RF69_MODE_STANDBY);
-  if (key != 0)
+  uint8_t validKey = key != 0 && strlen(key)!=0;
+  if (validKey)
   {
 #if defined(RF69_LISTENMODE_ENABLE)
     memcpy(_encryptKey, key, 16);
@@ -449,7 +450,7 @@ void RFM69::encrypt(const char* key) {
       _spi->transfer(key[i]);
     unselect();
   }
-  writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFE) | (key ? 1 : 0));
+  writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFE) | (validKey ? 1 : 0));
 }
 
 // get the received signal strength indicator (RSSI)
@@ -1211,4 +1212,4 @@ void RFM69::listenModeSendBurst( uint8_t targetNode, const void* buffer, uint8_t
   setMode(RF69_MODE_STANDBY);
   reinitRadio();
 }
-#endif
+#endif
\ No newline at end of file