diff --git a/fold.c b/fold.c
index 0d68b37..c7f6ae8 100644
--- a/fold.c
+++ b/fold.c
@@ -7,19 +7,22 @@
 
 #include "text.h"
 #include "util.h"
+#include "utf.h"
 
 static int    bflag = 0;
 static int    sflag = 0;
 static size_t width = 80;
 
 static void
-foldline(struct line *l) {
+foldline(struct line *l, const char *fname) {
 	size_t i, col, last, spacesect, len;
+	Rune r;
+	int runelen;
 
-	for (i = 0, last = 0, col = 0, spacesect = 0; i < l->len; i++) {
-		if (!UTF8_POINT(l->data[i]) && !bflag)
-			continue;
+	for (i = 0, last = 0, col = 0, spacesect = 0; i < l->len; i += runelen) {
 		if (col >= width && ((l->data[i] != '\r' && l->data[i] != '\b') || bflag)) {
+			if (bflag && col > width)
+				i -= runelen;	/* never split a character */
 			len = ((sflag && spacesect) ? spacesect : i) - last;
 			if (fwrite(l->data + last, 1, len, stdout) != len)
 				eprintf("fwrite <stdout>:");
@@ -29,8 +32,11 @@ foldline(struct line *l) {
 			col = 0;
 			spacesect = 0;
 		}
-		if (sflag && isspace(l->data[i]))
-			spacesect = i + 1;
+		runelen = charntorune(&r, l->data + i, l->len - i);
+		if (!runelen || r == Runeerror)
+			eprintf("charntorune: %s: invalid utf\n", fname);
+		if (sflag && isspacerune(r))
+			spacesect = i + runelen;
 		if (!bflag && iscntrl(l->data[i])) {
 			switch(l->data[i]) {
 			case '\b':
@@ -46,7 +52,7 @@ foldline(struct line *l) {
 				break;
 			}
 		} else {
-			col++;
+			col += bflag ? runelen : 1;
 		}
 	}
 	if (l->len - last)
@@ -62,7 +68,7 @@ fold(FILE *fp, const char *fname)
 
 	while ((len = getline(&line.data, &size, fp)) > 0) {
 		line.len = len;
-		foldline(&line);
+		foldline(&line, fname);
 	}
 	if (ferror(fp))
 		eprintf("getline %s:", fname);