diff --git a/src/option.c b/src/option.c
index 2146be7..2d22c4c 100644
--- a/src/option.c
+++ b/src/option.c
@@ -616,7 +616,7 @@
 			    (char_u *)"~",
 #endif
 					    (char_u *)0L} SCTX_INIT},
-    {"backupskip",  "bsk",  P_STRING|P_VI_DEF|P_ONECOMMA,
+    {"backupskip",  "bsk",  P_STRING|P_VI_DEF|P_ONECOMMA|P_NODUP,
 #ifdef FEAT_WILDIGN
 			    (char_u *)&p_bsk, PV_NONE,
 			    {(char_u *)"", (char_u *)0L}
@@ -4807,7 +4807,8 @@
 			     * hex numbers. */
 			    vim_str2nr(arg, NULL, &i, STR2NR_ALL,
 						     &value, NULL, 0, TRUE);
-			    if (i == 0 || (arg[i] != NUL && !VIM_ISWHITE(arg[i])))
+			    if (i == 0 || (arg[i] != NUL
+						      && !VIM_ISWHITE(arg[i])))
 			    {
 				errmsg = N_("E521: Number required after =");
 				goto skip;
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index 13de719..9d3065d 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -419,6 +419,15 @@
       call assert_true(found, var . ' (' . varvalue . ') not in option bsk: ' . &bsk)
     endif
   endfor
+
+  " Duplicates should be filtered out (option has P_NODUP)
+  let backupskip = &backupskip
+  set backupskip=
+  set backupskip+=/test/dir
+  set backupskip+=/other/dir
+  set backupskip+=/test/dir
+  call assert_equal('/test/dir,/other/dir', &backupskip)
+  let &backupskip = backupskip
 endfunc
 
 func Test_copy_winopt()
diff --git a/src/version.c b/src/version.c
index 7432f70..5c41f4f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1519,
+/**/
     1518,
 /**/
     1517,