diff --git a/include/fat.h b/include/fat.h
index c8eb7ccd2904c2e9977b252f4234d20854e29501..65da733aef36aa23132290ab0c61caec69fd6604 100644
--- a/include/fat.h
+++ b/include/fat.h
@@ -85,7 +85,9 @@
 			+ (mydata->fatsize != 32 ? 0 : \
 			  (FAT2CPU16((dent)->starthi) << 16)))
 #define CHECK_CLUST(x, fatsize) ((x) <= 1 || \
-				(x) >= ((fatsize) != 32 ? 0xfff0 : 0xffffff0))
+				(x) >= ((fatsize) != 32 ? \
+					((fatsize) != 16 ? 0xff0 : 0xfff0) : \
+					0xffffff0))
 
 typedef struct boot_sector {
 	__u8	ignored[3];	/* Bootstrap code */