diff --git a/include/driver/lm75.h b/include/driver/lm75.h
index 357be71cc57379691f99be67ae0d5ba086fe396c..c1a9ddf0c28f4f91f5bbb07af924433d27aa7f37 100644
--- a/include/driver/lm75.h
+++ b/include/driver/lm75.h
@@ -2,6 +2,8 @@
  * Copyright 2020 Daniel Friesel
  *
  * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Driver for LM75B Digital Temperature Sensor and Thermal Watchdog.
  */
 #ifndef LM75_H
 #define LM75_H
@@ -19,8 +21,8 @@ class LM75 {
 		float getTemp();
 		unsigned int getOS();
 		unsigned int getHyst();
-		void setOS(unsigned char os);
-		void setHyst(unsigned char hyst);
+		void setOS(signed char os);
+		void setHyst(signed char hyst);
 		void init();
 		void shutdown();
 };
diff --git a/src/driver/lm75.cc b/src/driver/lm75.cc
index 3fd148366e1c5ddb0812786e89c57512a2348dff..8aab05d8595c58b4b6f38a3a11172d97e3c1273c 100644
--- a/src/driver/lm75.cc
+++ b/src/driver/lm75.cc
@@ -2,6 +2,8 @@
  * Copyright 2020 Daniel Friesel
  *
  * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Driver for LM75B Digital Temperature Sensor and Thermal Watchdog.
  */
 #include "driver/lm75.h"
 #if defined(MULTIPASS_ARCH_HAS_I2C) && !defined(CONFIG_driver_softi2c)
@@ -40,7 +42,7 @@ unsigned int LM75::getHyst()
 	return rxbuf[0];
 }
 
-void LM75::setOS(unsigned char os)
+void LM75::setOS(signed char os)
 {
 	txbuf[0] = 0x03;
 	txbuf[1] = os;
@@ -48,7 +50,7 @@ void LM75::setOS(unsigned char os)
 	i2c.xmit(address, 3, txbuf, 0, rxbuf);
 }
 
-void LM75::setHyst(unsigned char hyst)
+void LM75::setHyst(signed char hyst)
 {
 	txbuf[0] = 0x02;
 	txbuf[1] = hyst;