diff --git a/source/ff.c b/source/ff.c
index 22a7cb9..7b3dbdc 100644
--- a/source/ff.c
+++ b/source/ff.c
@@ -6524,7 +6524,7 @@ static void putc_bfd (putbuff* pb, TCHAR c)
 			if ((BYTE)c < 0x80) break;					/* Single byte? */
 			if (((BYTE)c & 0xE0) == 0xC0) pb->ct = 1;	/* 2-byte sequence? */
 			if (((BYTE)c & 0xF0) == 0xE0) pb->ct = 2;	/* 3-byte sequence? */
-			if (((BYTE)c & 0xF1) == 0xF0) pb->ct = 3;	/* 4-byte sequence? */
+			if (((BYTE)c & 0xF8) == 0xF0) pb->ct = 3;	/* 4-byte sequence? */
 			return;
 		} else {				/* In the multi-byte sequence */
 			if (((BYTE)c & 0xC0) != 0x80) {	/* Broken sequence? */