diff --git a/block/vvfat.c b/block/vvfat.c
index 6d61c2e6c3..365332aa21 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -512,7 +512,7 @@ static inline uint8_t fat_chksum(const direntry_t* entry)
     for(i=0;i<11;i++) {
         unsigned char c;
 
-        c = (i <= 8) ? entry->name[i] : entry->extension[i-8];
+        c = (i < 8) ? entry->name[i] : entry->extension[i-8];
         chksum=(((chksum&0xfe)>>1)|((chksum&0x01)?0x80:0)) + c;
     }