diff --git a/src/hb-common.h b/src/hb-common.h
index fdceff9dc..37bbb2b14 100644
--- a/src/hb-common.h
+++ b/src/hb-common.h
@@ -86,8 +86,8 @@ typedef union _hb_var_int_t {
 
 typedef uint32_t hb_tag_t;
 
-#define HB_TAG(c1,c2,c3,c4) ((hb_tag_t)((((uint8_t)(c1))<<24)|(((uint8_t)(c2))<<16)|(((uint8_t)(c3))<<8)|((uint8_t)(c4))))
-#define HB_UNTAG(tag)   ((uint8_t)((tag)>>24)), ((uint8_t)((tag)>>16)), ((uint8_t)((tag)>>8)), ((uint8_t)(tag))
+#define HB_TAG(c1,c2,c3,c4) ((hb_tag_t)((((uint32_t)(c1)&0xFF)<<24)|(((uint32_t)(c2)&0xFF)<<16)|(((uint32_t)(c3)&0xFF)<<8)|((uint32_t)(c4)&0xFF)))
+#define HB_UNTAG(tag)   (((tag)>>24)&0xFF), (((tag)>>16)&0xFF), (((tag)>>8)&0xFF), ((tag)&0xFF)
 
 #define HB_TAG_NONE HB_TAG(0,0,0,0)
 #define HB_TAG_MAX HB_TAG(0xff,0xff,0xff,0xff)