diff --git a/bus.cpp b/bus.cpp
index 7e81f27..538c23d 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -416,7 +416,7 @@ uint16_t bus::read(const uint16_t addr_in, const word_mode_t word_mode, const rm
 	return temp;
 }
 
-void bus::setMMR0(int value)
+void bus::setMMR0(const uint16_t value)
 {
 	value &= ~(3 << 10);  // bit 10 & 11 always read as 0
 
diff --git a/bus.h b/bus.h
index 71baf0c..153edef 100644
--- a/bus.h
+++ b/bus.h
@@ -156,7 +156,7 @@ public:
 	uint16_t getMMR3() { return MMR3; }
 	void     clearMMR1();
 	void     addToMMR1(const int8_t delta, const uint8_t reg);
-	void     setMMR0(int value);
+	void     setMMR0(const uint16_t value);
 	void     setMMR0Bit(const int bit);
 	void     clearMMR0Bit(const int bit);
 	void     setMMR2(const uint16_t value);