diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 994ef0c..3384fe8 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -398,6 +398,7 @@
     colnr_T	end_col;
     int		sort_what = 0;
     int		format_found = 0;
+    int		change_occurred = FALSE; // Buffer contents changed.
 
     /* Sorting one line is really quick! */
     if (count <= 1)
@@ -616,12 +617,19 @@
     lnum = eap->line2;
     for (i = 0; i < count; ++i)
     {
-	s = ml_get(nrs[eap->forceit ? count - i - 1 : i].lnum);
+	linenr_T get_lnum = nrs[eap->forceit ? count - i - 1 : i].lnum;
+
+	// If the original line number of the line being placed is not the same
+	// as "lnum" (accounting for offset), we know that the buffer changed.
+	if (get_lnum + ((linenr_T)count - 1) != lnum)
+	    change_occurred = TRUE;
+
+	s = ml_get(get_lnum);
 	if (!unique || i == 0
 		|| (sort_ic ? STRICMP(s, sortbuf1) : STRCMP(s, sortbuf1)) != 0)
 	{
-	    /* Copy the line into a buffer, it may become invalid in
-	     * ml_append(). And it's needed for "unique". */
+	    // Copy the line into a buffer, it may become invalid in
+	    // ml_append(). And it's needed for "unique".
 	    STRCPY(sortbuf1, s);
 	    if (ml_append(lnum++, sortbuf1, (colnr_T)0, FALSE) == FAIL)
 		break;
@@ -644,7 +652,9 @@
 	mark_adjust(eap->line2 - deleted, eap->line2, (long)MAXLNUM, -deleted);
     else if (deleted < 0)
 	mark_adjust(eap->line2, MAXLNUM, -deleted, 0L);
-    changed_lines(eap->line1, 0, eap->line2 + 1, -deleted);
+
+    if (change_occurred || deleted != 0)
+	changed_lines(eap->line1, 0, eap->line2 + 1, -deleted);
 
     curwin->w_cursor.lnum = eap->line1;
     beginline(BL_WHITE | BL_FIX);