diff --git a/src/ops.c b/src/ops.c
index 3ee6e55..3989802 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -2429,8 +2429,13 @@
     {
 # ifdef FEAT_MBYTE
 	if (has_mbyte)
+	{
+	    int len = (*mb_ptr2len)(ml_get_pos(pos));
+
 	    /* we're counting bytes, not characters */
-	    todo -= (*mb_ptr2len)(ml_get_pos(pos)) - 1;
+	    if (len > 0)
+		todo -= len - 1;
+	}
 # endif
 	did_change |= swapchar(op_type, pos);
 	if (inc(pos) == -1)    /* at end of file */