diff --git a/Firmware/Filament_sensor.cpp b/Firmware/Filament_sensor.cpp
index 5b235f121..732ac6247 100644
--- a/Firmware/Filament_sensor.cpp
+++ b/Firmware/Filament_sensor.cpp
@@ -278,7 +278,9 @@ void IR_sensor_analog::voltUpdate(uint16_t raw) { // to be called from the ADC I
 }
 
 uint16_t IR_sensor_analog::getVoltRaw() {
-    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { return voltRaw; }
+    uint16_t ret;
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { ret = voltRaw; }
+    return ret;
 }
 
 const char *IR_sensor_analog::getIRVersionText() {
@@ -339,7 +341,9 @@ bool IR_sensor_analog::checkVoltage(uint16_t raw) {
 }
 
 bool IR_sensor_analog::getVoltReady() const {
-    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){ return voltReady; }
+    bool ret;
+    ATOMIC_BLOCK(ATOMIC_RESTORESTATE){ ret = voltReady; }
+    return ret;
 }
 
 void IR_sensor_analog::clearVoltReady(){
diff --git a/Firmware/mmu2.cpp b/Firmware/mmu2.cpp
index 95e234e74..365ac4b71 100644
--- a/Firmware/mmu2.cpp
+++ b/Firmware/mmu2.cpp
@@ -380,6 +380,8 @@ bool MMU2::set_filament_type(uint8_t index, uint8_t type) {
         return false;
     
     // @@TODO - this is not supported in the new MMU yet
+    index = index; // @@TODO
+    type = type; // @@TODO
     // cmd_arg = filamentType;
     // command(MMU_CMD_F0 + index);
 
diff --git a/Firmware/mmu2.h b/Firmware/mmu2.h
index 005653726..08fde19c0 100644
--- a/Firmware/mmu2.h
+++ b/Firmware/mmu2.h
@@ -279,9 +279,8 @@ private:
     /// unlike the mid-print ToolChange commands, which only load the first ~30mm and then the G-code takes over.
     bool loadingToNozzle;
     
-    uint8_t retryAttempts;
-
     bool inAutoRetry;
+    uint8_t retryAttempts;
 };
 
 /// following Marlin's way of doing stuff - one and only instance of MMU implementation in the code base
diff --git a/Firmware/mmu2_error_converter.cpp b/Firmware/mmu2_error_converter.cpp
index fd000226f..a4dd070df 100644
--- a/Firmware/mmu2_error_converter.cpp
+++ b/Firmware/mmu2_error_converter.cpp
@@ -132,24 +132,24 @@ uint16_t PrusaErrorCode(uint8_t i){
     return pgm_read_word(errorCodes + i);
 }
 
-const char * const PrusaErrorTitle(uint8_t i){
-    return (const char * const)pgm_read_ptr(errorTitles + i);
+const char * PrusaErrorTitle(uint8_t i){
+    return (const char *)pgm_read_ptr(errorTitles + i);
 }
 
-const char * const PrusaErrorDesc(uint8_t i){
-    return (const char * const)pgm_read_ptr(errorDescs + i);
+const char * PrusaErrorDesc(uint8_t i){
+    return (const char *)pgm_read_ptr(errorDescs + i);
 }
 
 uint8_t PrusaErrorButtons(uint8_t i){
     return pgm_read_byte(errorButtons + i);
 }
 
-const char * const PrusaErrorButtonTitle(uint8_t bi){
+const char * PrusaErrorButtonTitle(uint8_t bi){
     // -1 represents the hidden NoOperation button which is not drawn in any way
-    return (const char * const)pgm_read_ptr(btnOperation + bi - 1);
+    return (const char *)pgm_read_ptr(btnOperation + bi - 1);
 }
 
-const char * const PrusaErrorButtonMore(){
+const char * PrusaErrorButtonMore(){
     return _R(MSG_BTN_MORE);
 }
 
diff --git a/Firmware/mmu2_error_converter.h b/Firmware/mmu2_error_converter.h
index 597cc35a5..0e158aa2f 100644
--- a/Firmware/mmu2_error_converter.h
+++ b/Firmware/mmu2_error_converter.h
@@ -11,11 +11,11 @@ uint8_t PrusaErrorCodeIndex(uint16_t ec);
 
 /// @returns pointer to a PROGMEM string representing the Title of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
-const char * const PrusaErrorTitle(uint8_t i);
+const char * PrusaErrorTitle(uint8_t i);
 
 /// @returns pointer to a PROGMEM string representing the multi-page Description of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
-const char * const PrusaErrorDesc(uint8_t i);
+const char * PrusaErrorDesc(uint8_t i);
 
 /// @returns the actual numerical value of the Prusa-Error-Codes error
 /// @param i index of the error - obtained by calling ErrorCodeIndex
@@ -27,10 +27,10 @@ uint8_t PrusaErrorButtons(uint8_t i);
 
 /// @returns pointer to a PROGMEM string representing the Title of a button
 /// @param i index of the error - obtained by calling PrusaErrorButtons + extracting low or high nibble from the Btns pair
-const char * const PrusaErrorButtonTitle(uint8_t bi);
+const char * PrusaErrorButtonTitle(uint8_t bi);
 
 /// @returns pointer to a PROGMEM string representing the "More" button
-const char * const PrusaErrorButtonMore();
+const char * PrusaErrorButtonMore();
 
 /// Sets the selected button for later pick-up by the MMU state machine.
 /// Used to save the GUI selection/decoupling
diff --git a/Firmware/mmu2_progress_converter.cpp b/Firmware/mmu2_progress_converter.cpp
index b7d3fcf34..b44951385 100644
--- a/Firmware/mmu2_progress_converter.cpp
+++ b/Firmware/mmu2_progress_converter.cpp
@@ -62,11 +62,11 @@ static const char * const progressTexts[] PROGMEM = {
     _R(MSG_PROGRESS_FEED_FSENSOR)
 };
 
-const char * const ProgressCodeToText(uint16_t pc){
+const char * ProgressCodeToText(uint16_t pc){
     // @@TODO ?? a better fallback option?
     return ( pc <= (sizeof(progressTexts) / sizeof(progressTexts[0])) )
-       ? static_cast<const char * const>(pgm_read_ptr(&progressTexts[pc]))
-       : static_cast<const char * const>(pgm_read_ptr(&progressTexts[0]));
+       ? static_cast<const char *>(pgm_read_ptr(&progressTexts[pc]))
+       : static_cast<const char *>(pgm_read_ptr(&progressTexts[0]));
 }
 
 } // namespace MMU2
diff --git a/Firmware/mmu2_progress_converter.h b/Firmware/mmu2_progress_converter.h
index 72dcc031b..19cb1e3fc 100644
--- a/Firmware/mmu2_progress_converter.h
+++ b/Firmware/mmu2_progress_converter.h
@@ -4,6 +4,6 @@
 
 namespace MMU2 {
 
-const char * const ProgressCodeToText(uint16_t pc);
+const char * ProgressCodeToText(uint16_t pc);
 
 }
diff --git a/Firmware/mmu2_protocol.cpp b/Firmware/mmu2_protocol.cpp
index 16fe69f4a..c79443238 100644
--- a/Firmware/mmu2_protocol.cpp
+++ b/Firmware/mmu2_protocol.cpp
@@ -112,6 +112,10 @@ DecodeStatus Protocol::DecodeRequest(uint8_t c) {
                 rqState = RequestStates::Code;
                 return DecodeStatus::MessageCompleted;
             }
+        } else {
+            requestMsg.code = RequestMsgCodes::unknown;
+            rqState = RequestStates::Error;
+            return DecodeStatus::Error;
         }
     default: //case error:
         if (IsNewLine(c)) {
diff --git a/Firmware/mmu2_reporting.cpp b/Firmware/mmu2_reporting.cpp
index 37b316d4f..d63bb681e 100644
--- a/Firmware/mmu2_reporting.cpp
+++ b/Firmware/mmu2_reporting.cpp
@@ -11,14 +11,14 @@
 
 namespace MMU2 {
 
-const char * const ProgressCodeToText(uint16_t pc); // we may join progress convertor and reporter together
+const char * ProgressCodeToText(uint16_t pc); // we may join progress convertor and reporter together
 
-void BeginReport(CommandInProgress cip, uint16_t ec) {
+void BeginReport(CommandInProgress /*cip*/, uint16_t ec) {
     custom_message_type = CustomMsg::MMUProgress;
     lcd_setstatuspgm( _T(ProgressCodeToText(ec)) );
 }
 
-void EndReport(CommandInProgress cip, uint16_t ec) {
+void EndReport(CommandInProgress /*cip*/, uint16_t /*ec*/) {
     // clear the status msg line - let the printed filename get visible again
     custom_message_type = CustomMsg::Status;
 }
diff --git a/Firmware/mmu2_serial.cpp b/Firmware/mmu2_serial.cpp
index 5ac8e3e29..f26f44f41 100644
--- a/Firmware/mmu2_serial.cpp
+++ b/Firmware/mmu2_serial.cpp
@@ -19,7 +19,7 @@ void MMU2Serial::flush() {
     // @@TODO - clear the output buffer
 }
 
-size_t MMU2Serial::write(const uint8_t *buffer, size_t size) {
+void MMU2Serial::write(const uint8_t *buffer, size_t size) {
     while(size--){
         fputc(*buffer, uart2io);
         ++buffer;
diff --git a/Firmware/mmu2_serial.h b/Firmware/mmu2_serial.h
index 176a8f336..43066af18 100644
--- a/Firmware/mmu2_serial.h
+++ b/Firmware/mmu2_serial.h
@@ -12,7 +12,7 @@ public:
     void close();
     int read();
     void flush();
-    size_t write(const uint8_t *buffer, size_t size);
+    void write(const uint8_t *buffer, size_t size);
 };
 
 extern MMU2Serial mmu2Serial;