diff --git a/src/misc1.c b/src/misc1.c
index fbb1081..dce912c 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -1427,8 +1427,12 @@
 	/* Postpone calling changed_lines(), because it would mess up folding
 	 * with markers.
 	 * Skip mark_adjust when adding a line after the last one, there can't
-	 * be marks there. */
-	if (curwin->w_cursor.lnum + 1 < curbuf->b_ml.ml_line_count)
+	 * be marks there. But still needed in diff mode. */
+	if (curwin->w_cursor.lnum + 1 < curbuf->b_ml.ml_line_count
+#ifdef FEAT_DIFF
+		|| curwin->w_p_diff
+#endif
+	    )
 	    mark_adjust(curwin->w_cursor.lnum + 1, (linenr_T)MAXLNUM, 1L, 0L);
 	did_append = TRUE;
     }
@@ -2863,8 +2867,12 @@
 appended_lines_mark(linenr_T lnum, long count)
 {
     /* Skip mark_adjust when adding a line after the last one, there can't
-     * be marks there. */
-    if (lnum + count < curbuf->b_ml.ml_line_count)
+     * be marks there. But it's still needed in diff mode. */
+    if (lnum + count < curbuf->b_ml.ml_line_count
+#ifdef FEAT_DIFF
+	    || curwin->w_p_diff
+#endif
+	)
 	mark_adjust(lnum + 1, (linenr_T)MAXLNUM, count, 0L);
     changed_lines(lnum + 1, 0, lnum + 1, count);
 }