diff --git a/sys/src/9/port/lib.h b/sys/src/9/port/lib.h
index 1dbccbcc5..7d58fed9d 100644
--- a/sys/src/9/port/lib.h
+++ b/sys/src/9/port/lib.h
@@ -35,11 +35,11 @@ extern	int	cistrncmp(char*, char*, int);
 
 enum
 {
-	UTFmax		= 3,	/* maximum bytes per rune */
-	Runesync	= 0x80,	/* cannot represent part of a UTF sequence */
-	Runeself	= 0x80,	/* rune and UTF sequences are the same (<) */
+	UTFmax		= 4,		/* maximum bytes per rune */
+	Runesync	= 0x80,		/* cannot represent part of a UTF sequence */
+	Runeself	= 0x80,		/* rune and UTF sequences are the same (<) */
 	Runeerror	= 0xFFFD,	/* decoding error in UTF */
-	Runemax		= 0xFFFF,	/* 16 bit rune */
+	Runemax		= 0x10FFFF,	/* 21 bit rune */
 };
 
 /*