diff --git a/src/eval.c b/src/eval.c
index 146348d..a3fe2a2 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -19774,7 +19774,12 @@
 	    charlen = get_tv_number(&argvars[2]);
 	    while (charlen > 0 && nbyte + len < slen)
 	    {
-		len += mb_char2len(p[nbyte + len]);
+		int off = nbyte + len;
+
+		if (off < 0)
+		    len += 1;
+		else
+		    len += mb_char2len(p[off]);
 		--charlen;
 	    }
 	}
diff --git a/src/version.c b/src/version.c
index 9aa400e..adbb46a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1779,
+/**/
     1778,
 /**/
     1777,