diff --git a/communication/decoder.cpp b/communication/decoder.cpp
index bead06c..cd9b5cd 100644
--- a/communication/decoder.cpp
+++ b/communication/decoder.cpp
@@ -13,10 +13,10 @@
 
 using namespace icsneo;
 
-uint64_t Decoder::GetUInt64FromLEBytes(uint8_t* bytes) {
+uint64_t Decoder::GetUInt64FromLEBytes(const uint8_t* bytes) {
 	uint64_t ret = 0;
 	for(int i = 0; i < 8; i++)
-		ret |= (bytes[i] << (i * 8));
+		ret |= (uint64_t(bytes[i]) << (i * 8));
 	return ret;
 }
 
diff --git a/include/icsneo/communication/decoder.h b/include/icsneo/communication/decoder.h
index ca5a651..dd5792e 100644
--- a/include/icsneo/communication/decoder.h
+++ b/include/icsneo/communication/decoder.h
@@ -16,7 +16,7 @@ namespace icsneo {
 
 class Decoder {
 public:
-	static uint64_t GetUInt64FromLEBytes(uint8_t* bytes);
+	static uint64_t GetUInt64FromLEBytes(const uint8_t* bytes);
 
 	Decoder(device_eventhandler_t report) : report(report) {}
 	bool decode(std::shared_ptr<Message>& result, const std::shared_ptr<Packet>& packet);