diff --git a/os/src/drivers/atapi/endian.h b/os/src/drivers/atapi/endian.h
index 0a1824c739..61b5c037e4 100644
--- a/os/src/drivers/atapi/endian.h
+++ b/os/src/drivers/atapi/endian.h
@@ -16,11 +16,11 @@
 template <typename T>
 inline T bswap32(T x)
 {
-	char v[4] = {
-		(x & 0xff000000) >> 24,
-		(x & 0x00ff0000) >> 16,
-		(x & 0x0000ff00) >>  8,
-		(x & 0x000000ff) >>  0,
+	unsigned char v[4] = {
+		(unsigned char)((x & 0xff000000) >> 24),
+		(unsigned char)((x & 0x00ff0000) >> 16),
+		(unsigned char)((x & 0x0000ff00) >>  8),
+		(unsigned char)((x & 0x000000ff) >>  0),
 	};
 	return *(T *)v;
 }
diff --git a/os/src/server/nitpicker/data/big_mouse.h b/os/src/server/nitpicker/data/big_mouse.h
index 6f7fa86e0e..75e57ddf25 100644
--- a/os/src/server/nitpicker/data/big_mouse.h
+++ b/os/src/server/nitpicker/data/big_mouse.h
@@ -12,7 +12,7 @@
  */
 
 static struct {
-	short w, h, pixels[16][16];
+	unsigned short w, h, pixels[16][16];
 } big_mouse = {
 	16,16,
 	{