diff --git a/fournsnes.c b/fournsnes.c
index 106f311..c54dc08 100644
--- a/fournsnes.c
+++ b/fournsnes.c
@@ -57,7 +57,7 @@
 /*********** prototypes *************/
 static void fournsnesInit(void);
 static void fournsnesUpdate(void);
-static char fournsnesChanged(char report_id);
+static char fournsnesChanged(unsigned char report_id);
 static char fournsnesBuildReport(unsigned char *reportBuffer, char report_id);
 
 
@@ -480,7 +480,7 @@ static void fournsnesUpdate(void)
 
 }
 
-static char fournsnesChanged(char report_id)
+static char fournsnesChanged(unsigned char report_id)
 {
 	report_id--; // first report is 1
 
diff --git a/gamepad.h b/gamepad.h
index 5b07963..82891a7 100644
--- a/gamepad.h
+++ b/gamepad.h
@@ -14,7 +14,7 @@ typedef struct {
 	void (*init)(void);
 	void (*update)(void);
 
-	char (*changed)(char id);
+	char (*changed)(unsigned char id);
 	/**
 	 * \param id Controller id (starting at 1 to match report IDs)
 	 * \return The number of bytes written to buf.