diff --git a/src/evalfunc.c b/src/evalfunc.c
index 110935df3d..1764f414ea 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1975,7 +1975,7 @@ f_deepcopy(typval_T *argvars, typval_T *rettv)
     int		copyID;
 
     if (argvars[1].v_type != VAR_UNKNOWN)
-	noref = (int)tv_get_number_chk(&argvars[1], NULL);
+	noref = (int)tv_get_bool_chk(&argvars[1], NULL);
     if (noref < 0 || noref > 1)
 	emsg(_(e_invarg));
     else
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index 8db7b3f168..694ba0a410 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -348,7 +348,7 @@ func Test_dict_deepcopy()
   let l[1] = l2
   let l3 = deepcopy(l2)
   call assert_true(l3[1] is l3[2])
-  call assert_fails("call deepcopy([1, 2], 2)", 'E474:')
+  call assert_fails("call deepcopy([1, 2], 2)", 'E1023:')
 endfunc
 
 " Locked variables
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 828dbba3d0..8651ef8ebd 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1272,6 +1272,8 @@ def Test_copy_return_type()
     res += n
   endfor
   assert_equal(6, res)
+
+  dl = deepcopy([1, 2, 3], true)
 enddef
 
 def Test_extend_return_type()
diff --git a/src/version.c b/src/version.c
index b7b5d272e8..8ebf9a7167 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1600,
 /**/
     1599,
 /**/