diff --git a/Software/src/lib/eModbus-eModbus/RTUutils.cpp b/Software/src/lib/eModbus-eModbus/RTUutils.cpp
index c92d0ffd..fc4eaadf 100644
--- a/Software/src/lib/eModbus-eModbus/RTUutils.cpp
+++ b/Software/src/lib/eModbus-eModbus/RTUutils.cpp
@@ -440,7 +440,7 @@ ModbusMessage RTUutils::receive(uint8_t caller, Stream& serial, uint32_t timeout
 }
 
 // Lower 7 bit ASCII characters - all invalid are set to 0xFF
-const char RTUutils::ASCIIread[] = { 
+const uint8_t RTUutils::ASCIIread[] = { 
   /* 00-07 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
   /* 08-0F */ 0xFF, 0xFF, 0xF2, 0xFF, 0xFF, 0xF1, 0xFF, 0xFF,  // LF + CR
   /* 10-17 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
diff --git a/Software/src/lib/eModbus-eModbus/RTUutils.h b/Software/src/lib/eModbus-eModbus/RTUutils.h
index e3f41be3..2306d4a4 100644
--- a/Software/src/lib/eModbus-eModbus/RTUutils.h
+++ b/Software/src/lib/eModbus-eModbus/RTUutils.h
@@ -60,7 +60,7 @@ static void prepareHardwareSerial(HardwareSerial& s, uint16_t bufferSize = 260)
 protected:
 // Printable characters for ASCII protocol: 012345678ABCDEF
   static const char ASCIIwrite[];
-  static const char ASCIIread[];
+  static const uint8_t ASCIIread[];
 
   RTUutils() = delete;