diff --git a/cpu/mpc8xx/i2c.c b/cpu/mpc8xx/i2c.c
index baa3552..682db53 100644
--- a/cpu/mpc8xx/i2c.c
+++ b/cpu/mpc8xx/i2c.c
@@ -724,7 +724,7 @@
 uchar
 i2c_reg_read(uchar i2c_addr, uchar reg)
 {
-	char buf;
+	uchar buf;
 
 	i2c_init(CFG_I2C_SPEED, CFG_I2C_SLAVE);