diff --git a/drivers/usb/misc/sisusbvga/sisusb_struct.h b/drivers/usb/misc/sisusbvga/sisusb_struct.h
index 3df64d2a9d43d..a86032a26d36d 100644
--- a/drivers/usb/misc/sisusbvga/sisusb_struct.h
+++ b/drivers/usb/misc/sisusbvga/sisusb_struct.h
@@ -91,7 +91,7 @@ struct SiS_Ext {
 	unsigned char VB_ExtTVYFilterIndex;
 	unsigned char VB_ExtTVYFilterIndexROM661;
 	unsigned char REFindex;
-	char ROMMODEIDX661;
+	signed char ROMMODEIDX661;
 };
 
 struct SiS_Ext2 {
diff --git a/drivers/video/fbdev/sis/vstruct.h b/drivers/video/fbdev/sis/vstruct.h
index ea94d214dcff5..d7a14e63ba5ab 100644
--- a/drivers/video/fbdev/sis/vstruct.h
+++ b/drivers/video/fbdev/sis/vstruct.h
@@ -148,7 +148,7 @@ struct SiS_Ext {
 	unsigned char  VB_ExtTVYFilterIndex;
 	unsigned char  VB_ExtTVYFilterIndexROM661;
 	unsigned char  REFindex;
-	char           ROMMODEIDX661;
+	signed char    ROMMODEIDX661;
 };
 
 struct SiS_Ext2 {