diff --git a/lib/charset.c b/lib/charset.c
index b184275..5e4c4f9 100644
--- a/lib/charset.c
+++ b/lib/charset.c
@@ -444,14 +444,14 @@
 
 size_t u16_strlcat(u16 *dest, const u16 *src, size_t count)
 {
-	size_t destlen = u16_strlen(dest);
+	size_t destlen = u16_strnlen(dest, count);
 	size_t srclen = u16_strlen(src);
-	size_t ret = destlen + srclen + 1;
+	size_t ret = destlen + srclen;
 
 	if (destlen >= count)
 		return ret;
-	if (ret > count)
-		srclen -= ret - count;
+	if (ret >= count)
+		srclen -= (ret - count + 1);
 	memcpy(&dest[destlen], src, 2 * srclen);
 	dest[destlen + srclen] = 0x0000;
 
diff --git a/test/unicode_ut.c b/test/unicode_ut.c
index b27d711..a9356e2 100644
--- a/test/unicode_ut.c
+++ b/test/unicode_ut.c
@@ -808,12 +808,12 @@
 	/* dest and src are empty string */
 	memset(buf, 0, sizeof(buf));
 	ret = u16_strlcat(buf, &null_src, sizeof(buf));
-	ut_asserteq(1, ret);
+	ut_asserteq(0, ret);
 
 	/* dest is empty string */
 	memset(buf, 0, sizeof(buf));
 	ret = u16_strlcat(buf, src, sizeof(buf));
-	ut_asserteq(5, ret);
+	ut_asserteq(4, ret);
 	ut_assert(!unicode_test_u16_strcmp(buf, src, 40));
 
 	/* src is empty string */
@@ -821,14 +821,14 @@
 	buf[39] = 0;
 	memcpy(buf, dest, sizeof(dest));
 	ret = u16_strlcat(buf, &null_src, sizeof(buf));
-	ut_asserteq(6, ret);
+	ut_asserteq(5, ret);
 	ut_assert(!unicode_test_u16_strcmp(buf, dest, 40));
 
 	for (i = 0; i <= 40; i++) {
 		memset(buf, 0xCD, (sizeof(buf) - sizeof(u16)));
 		buf[39] = 0;
 		memcpy(buf, dest, sizeof(dest));
-		expected = 10;
+		expected = min(5, i) + 4;
 		ret = u16_strlcat(buf, src, i);
 		ut_asserteq(expected, ret);
 		if (i <= 6) {