diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index dae1e2e71..d1bb603b2 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -222,7 +222,7 @@ void FurnaceGUI::encodeMMLStr(String& target, unsigned char* macro, unsigned cha
   }
 }
 
-void FurnaceGUI::encodeMMLStr(String& target, int* macro, unsigned char macroLen, signed char macroLoop) {
+void FurnaceGUI::encodeMMLStr(String& target, int* macro, int macroLen, int macroLoop) {
   target="";
   char buf[32];
   for (int i=0; i<macroLen; i++) {
diff --git a/src/gui/gui.h b/src/gui/gui.h
index 416a17c6e..96cbe5467 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -391,7 +391,7 @@ class FurnaceGUI {
 
   void applyUISettings();
 
-  void encodeMMLStr(String& target, int* macro, unsigned char macroLen, signed char macroLoop);
+  void encodeMMLStr(String& target, int* macro, int macroLen, int macroLoop);
   void encodeMMLStr(String& target, unsigned char* macro, unsigned char macroLen, signed char macroLoop);
   void decodeMMLStr(String& source, unsigned char* macro, unsigned char& macroLen, signed char& macroLoop, int macroMin, int macroMax);
   void decodeMMLStr(String& source, int* macro, unsigned char& macroLen, signed char& macroLoop, int macroMin, int macroMax);