diff --git a/src/errors.h b/src/errors.h
index 13d947b..9c8d593 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3372,4 +3372,6 @@
 	INIT(= N_("E1326: Member not found on object \"%s\": %s"));
 EXTERN char e_object_required_found_str[]
 	INIT(= N_("E1327: Object required, found %s"));
+EXTERN char e_constructor_default_value_must_be_vnone_str[]
+	INIT(= N_("E1328: Constructor default value must be v:none: %s"));
 #endif
diff --git a/src/proto/vim9instr.pro b/src/proto/vim9instr.pro
index e26ca25..eb7baab 100644
--- a/src/proto/vim9instr.pro
+++ b/src/proto/vim9instr.pro
@@ -47,7 +47,7 @@
 int generate_DEF(cctx_T *cctx, char_u *name, size_t len);
 int generate_JUMP(cctx_T *cctx, jumpwhen_T when, int where);
 int generate_WHILE(cctx_T *cctx, int funcref_idx);
-int generate_JUMP_IF_ARG_SET(cctx_T *cctx, int arg_off);
+int generate_JUMP_IF_ARG(cctx_T *cctx, isntype_T isn_type, int arg_off);
 int generate_FOR(cctx_T *cctx, int loop_idx);
 int generate_ENDLOOP(cctx_T *cctx, loop_info_T *loop_info);
 int generate_TRYCONT(cctx_T *cctx, int levels, int where);
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index d444af0..3f66f3f 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -182,5 +182,56 @@
   v9.CheckScriptSuccess(lines)
 enddef
 
+def Test_class_default_new()
+  var lines =<< trim END
+      vim9script
+
+      class TextPosition
+        this.lnum: number = 1
+        this.col: number = 1
+      endclass
+
+      var pos = TextPosition.new()
+      assert_equal(1, pos.lnum)
+      assert_equal(1, pos.col)
+
+      pos = TextPosition.new(v:none, v:none)
+      assert_equal(1, pos.lnum)
+      assert_equal(1, pos.col)
+
+      pos = TextPosition.new(3, 22)
+      assert_equal(3, pos.lnum)
+      assert_equal(22, pos.col)
+
+      pos = TextPosition.new(v:none, 33)
+      assert_equal(1, pos.lnum)
+      assert_equal(33, pos.col)
+  END
+  v9.CheckScriptSuccess(lines)
+
+  lines =<< trim END
+      vim9script
+      class Person
+        this.name: string
+        this.age: number = 42
+        this.education: string = "unknown"
+
+        def new(this.name, this.age = v:none, this.education = v:none)
+        enddef
+      endclass
+
+      var piet = Person.new("Piet")
+      assert_equal("Piet", piet.name)
+      assert_equal(42, piet.age)
+      assert_equal("unknown", piet.education)
+
+      var chris = Person.new("Chris", 4, "none")
+      assert_equal("Chris", chris.name)
+      assert_equal(4, chris.age)
+      assert_equal("none", chris.education)
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker
diff --git a/src/userfunc.c b/src/userfunc.c
index 9ac1274..f3e4757 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -224,7 +224,6 @@
     char_u	*p;
     int		c;
     int		any_default = FALSE;
-    char_u	*expr;
     char_u	*whitep = *argp;
 
     if (newargs != NULL)
@@ -302,6 +301,34 @@
 	    arg = p;
 	    while (ASCII_ISALNUM(*p) || *p == '_')
 		++p;
+	    char_u *argend = p;
+
+	    if (*skipwhite(p) == '=')
+	    {
+		char_u *defval = skipwhite(skipwhite(p) + 1);
+		if (STRNCMP(defval, "v:none", 6) != 0)
+		{
+		    semsg(_(e_constructor_default_value_must_be_vnone_str), p);
+		    goto err_ret;
+		}
+		any_default = TRUE;
+		p = defval + 6;
+
+		if (ga_grow(default_args, 1) == FAIL)
+		    goto err_ret;
+
+		char_u *expr = vim_strsave((char_u *)"v:none");
+		if (expr == NULL)
+		    goto err_ret;
+		((char_u **)(default_args->ga_data))
+						 [default_args->ga_len] = expr;
+		default_args->ga_len++;
+	    }
+	    else if (any_default)
+	    {
+		emsg(_(e_non_default_argument_follows_default_argument));
+		goto err_ret;
+	    }
 
 	    // TODO: check the argument is indeed a member
 	    if (newargs != NULL && ga_grow(newargs, 1) == FAIL)
@@ -309,7 +336,7 @@
 	    if (newargs != NULL)
 	    {
 		((char_u **)(newargs->ga_data))[newargs->ga_len] =
-						    vim_strnsave(arg, p - arg);
+					       vim_strnsave(arg, argend - arg);
 		newargs->ga_len++;
 
 		if (argtypes != NULL && ga_grow(argtypes, 1) == OK)
@@ -322,15 +349,22 @@
 		    if (ga_grow(newlines, 1) == OK)
 		    {
 			// "this.name = name"
-			int len = 5 + (p - arg) + 3 + (p - arg) + 1;
+			int len = 5 + (argend - arg) + 3 + (argend - arg) + 1;
+			if (any_default)
+			    len += 14 + 10;
 			char_u *assignment = alloc(len);
 			if (assignment != NULL)
 			{
-			    c = *p;
-			    *p = NUL;
-			    vim_snprintf((char *)assignment, len,
+			    c = *argend;
+			    *argend = NUL;
+			    if (any_default)
+				vim_snprintf((char *)assignment, len,
+						"ifargisset %d this.%s = %s",
+					   default_args->ga_len - 1, arg, arg);
+			    else
+				vim_snprintf((char *)assignment, len,
 						     "this.%s = %s", arg, arg);
-			    *p = c;
+			    *argend = c;
 			    ((char_u **)(newlines->ga_data))[
 					      newlines->ga_len++] = assignment;
 			}
@@ -361,7 +395,7 @@
 		// find the end of the expression (doesn't evaluate it)
 		any_default = TRUE;
 		p = skipwhite(np + 1);
-		expr = p;
+		char_u *expr = p;
 		if (eval1(&p, &rettv, NULL) != FAIL)
 		{
 		    if (!skip)
diff --git a/src/version.c b/src/version.c
index 362cd43..fbc5956 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1053,
+/**/
     1052,
 /**/
     1051,
diff --git a/src/vim9.h b/src/vim9.h
index c1d11fc..bddeb15 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -124,6 +124,8 @@
     ISN_JUMP,	    // jump if condition is matched isn_arg.jump
     ISN_JUMP_IF_ARG_SET, // jump if argument is already set, uses
 			 // isn_arg.jumparg
+    ISN_JUMP_IF_ARG_NOT_SET, // jump if argument is not set, uses
+			 // isn_arg.jumparg
 
     // loop
     ISN_FOR,	    // get next item from a list, uses isn_arg.forloop
@@ -260,7 +262,7 @@
     int		jump_where;	// position to jump to
 } jump_T;
 
-// arguments to ISN_JUMP_IF_ARG_SET
+// arguments to ISN_JUMP_IF_ARG_SET and ISN_JUMP_IF_ARG_NOT_SET
 typedef struct {
     int		jump_arg_off;	// argument index, negative
     int		jump_where;	// position to jump to
diff --git a/src/vim9class.c b/src/vim9class.c
index c8cea3c..74a9bf3 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -269,6 +269,7 @@
 		ga_concat(&fga, (char_u *)"this.");
 		objmember_T *m = cl->class_obj_members + i;
 		ga_concat(&fga, (char_u *)m->om_name);
+		ga_concat(&fga, (char_u *)" = v:none");
 	    }
 	    ga_concat(&fga, (char_u *)")\nenddef\n");
 	    ga_append(&fga, NUL);
diff --git a/src/vim9compile.c b/src/vim9compile.c
index e27bf29..43bda5f 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2195,8 +2195,13 @@
  * Return "arg" if it does not look like a variable list.
  */
     static char_u *
-compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
+compile_assignment(
+	char_u	    *arg_start,
+	exarg_T	    *eap,
+	cmdidx_T    cmdidx,
+	cctx_T	    *cctx)
 {
+    char_u	*arg = arg_start;
     char_u	*var_start;
     char_u	*p;
     char_u	*end = arg;
@@ -2206,6 +2211,7 @@
     int		semicolon = 0;
     int		did_generate_slice = FALSE;
     garray_T	*instr = &cctx->ctx_instr;
+    int		jump_instr_idx = instr->ga_len;
     char_u	*op;
     int		oplen = 0;
     int		heredoc = FALSE;
@@ -2216,6 +2222,23 @@
     lhs_T	lhs;
     long	start_lnum = SOURCING_LNUM;
 
+    int		has_arg_is_set_prefix = STRNCMP(arg, "ifargisset ", 11) == 0;
+    if (has_arg_is_set_prefix)
+    {
+	arg += 11;
+	int def_idx = getdigits(&arg);
+	arg = skipwhite(arg);
+
+	// Use a JUMP_IF_ARG_NOT_SET instruction to skip if the value was not
+	// given and the default value is "v:none".
+	int off = STACK_FRAME_SIZE + (cctx->ctx_ufunc->uf_va_name != NULL
+								      ? 1 : 0);
+	int count = cctx->ctx_ufunc->uf_def_args.ga_len;
+	if (generate_JUMP_IF_ARG(cctx, ISN_JUMP_IF_ARG_NOT_SET,
+						def_idx - count - off) == FAIL)
+	    goto theend;
+    }
+
     // Skip over the "varname" or "[varname, varname]" to get to any "=".
     p = skip_var_list(arg, TRUE, &var_count, &semicolon, TRUE);
     if (p == NULL)
@@ -2636,6 +2659,13 @@
 
 	if (var_idx + 1 < var_count)
 	    var_start = skipwhite(lhs.lhs_end + 1);
+
+	if (has_arg_is_set_prefix)
+	{
+	    // set instruction index in JUMP_IF_ARG_SET to here
+	    isn_T *isn = ((isn_T *)instr->ga_data) + jump_instr_idx;
+	    isn->isn_arg.jumparg.jump_where = instr->ga_len;
+	}
     }
 
     // For "[var, var] = expr" drop the "expr" value.
@@ -2711,9 +2741,9 @@
 	}
     }
 
-    if (*eap->cmd == '[')
+    // might be "[var, var] = expr" or "ifargisset this.member = expr"
+    if (*eap->cmd == '[' || STRNCMP(eap->cmd, "ifargisset ", 11) == 0)
     {
-	// might be "[var, var] = expr"
 	*line = compile_assignment(eap->cmd, eap, CMD_SIZE, cctx);
 	if (*line == NULL)
 	    return FAIL;
@@ -2994,7 +3024,6 @@
 	int	count = ufunc->uf_def_args.ga_len;
 	int	first_def_arg = ufunc->uf_args.ga_len - count;
 	int	i;
-	char_u	*arg;
 	int	off = STACK_FRAME_SIZE + (ufunc->uf_va_name != NULL ? 1 : 0);
 	int	did_set_arg_type = FALSE;
 
@@ -3002,23 +3031,27 @@
 	SOURCING_LNUM = 0;  // line number unknown
 	for (i = 0; i < count; ++i)
 	{
+	    char_u *arg = ((char_u **)(ufunc->uf_def_args.ga_data))[i];
+	    if (STRCMP(arg, "v:none") == 0)
+		// "arg = v:none" means the argument is optional without
+		// setting a value when the argument is missing.
+		continue;
+
 	    type_T	*val_type;
 	    int		arg_idx = first_def_arg + i;
 	    where_T	where = WHERE_INIT;
-	    int		r;
 	    int		jump_instr_idx = instr->ga_len;
 	    isn_T	*isn;
 
 	    // Use a JUMP_IF_ARG_SET instruction to skip if the value was given.
-	    if (generate_JUMP_IF_ARG_SET(&cctx, i - count - off) == FAIL)
+	    if (generate_JUMP_IF_ARG(&cctx, ISN_JUMP_IF_ARG_SET,
+						      i - count - off) == FAIL)
 		goto erret;
 
 	    // Make sure later arguments are not found.
 	    ufunc->uf_args_visible = arg_idx;
 
-	    arg = ((char_u **)(ufunc->uf_def_args.ga_data))[i];
-	    r = compile_expr0(&arg, &cctx);
-
+	    int r = compile_expr0(&arg, &cctx);
 	    if (r == FAIL)
 		goto erret;
 
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 6a6ec41..1a8058a 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2068,7 +2068,7 @@
 }
 
 /*
- * Store a value in a list, dict or blob variable.
+ * Store a value in a list, dict, blob or object variable.
  * Returns OK, FAIL or NOTDONE (uncatchable error).
  */
     static int
@@ -2177,9 +2177,9 @@
 	{
 	    long	    lidx = (long)tv_idx->vval.v_number;
 	    blob_T	    *blob = tv_dest->vval.v_blob;
-	    varnumber_T nr;
-	    int	    error = FALSE;
-	    int	    len;
+	    varnumber_T	    nr;
+	    int		    error = FALSE;
+	    int		    len;
 
 	    if (blob == NULL)
 	    {
@@ -2209,6 +2209,7 @@
 	    long	    idx = (long)tv_idx->vval.v_number;
 	    object_T	    *obj = tv_dest->vval.v_object;
 	    typval_T	    *otv = (typval_T *)(obj + 1);
+	    clear_tv(&otv[idx]);
 	    otv[idx] = *tv;
 	}
 	else
@@ -4293,10 +4294,12 @@
 	    // Jump if an argument with a default value was already set and not
 	    // v:none.
 	    case ISN_JUMP_IF_ARG_SET:
+	    case ISN_JUMP_IF_ARG_NOT_SET:
 		tv = STACK_TV_VAR(iptr->isn_arg.jumparg.jump_arg_off);
-		if (tv->v_type != VAR_UNKNOWN
-			&& !(tv->v_type == VAR_SPECIAL
-					    && tv->vval.v_number == VVAL_NONE))
+		int arg_set = tv->v_type != VAR_UNKNOWN
+				&& !(tv->v_type == VAR_SPECIAL
+					    && tv->vval.v_number == VVAL_NONE);
+		if (iptr->isn_type == ISN_JUMP_IF_ARG_SET ? arg_set : !arg_set)
 		    ectx->ec_iidx = iptr->isn_arg.jumparg.jump_where;
 		break;
 
@@ -6633,6 +6636,12 @@
 						iptr->isn_arg.jump.jump_where);
 		break;
 
+	    case ISN_JUMP_IF_ARG_NOT_SET:
+		smsg("%s%4d JUMP_IF_ARG_NOT_SET arg[%d] -> %d", pfx, current,
+			 iptr->isn_arg.jumparg.jump_arg_off + STACK_FRAME_SIZE,
+						iptr->isn_arg.jump.jump_where);
+		break;
+
 	    case ISN_FOR:
 		{
 		    forloop_T *forloop = &iptr->isn_arg.forloop;
diff --git a/src/vim9instr.c b/src/vim9instr.c
index 49f8c52..47114f0 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -1408,15 +1408,15 @@
 }
 
 /*
- * Generate an ISN_JUMP_IF_ARG_SET instruction.
+ * Generate an ISN_JUMP_IF_ARG_SET or ISN_JUMP_IF_ARG_NOT_SET instruction.
  */
     int
-generate_JUMP_IF_ARG_SET(cctx_T *cctx, int arg_off)
+generate_JUMP_IF_ARG(cctx_T *cctx, isntype_T isn_type, int arg_off)
 {
     isn_T	*isn;
 
     RETURN_OK_IF_SKIP(cctx);
-    if ((isn = generate_instr(cctx, ISN_JUMP_IF_ARG_SET)) == NULL)
+    if ((isn = generate_instr(cctx, isn_type)) == NULL)
 	return FAIL;
     isn->isn_arg.jumparg.jump_arg_off = arg_off;
     // jump_where is set later
@@ -2479,6 +2479,7 @@
 	case ISN_GETITEM:
 	case ISN_GET_OBJ_MEMBER:
 	case ISN_JUMP:
+	case ISN_JUMP_IF_ARG_NOT_SET:
 	case ISN_JUMP_IF_ARG_SET:
 	case ISN_LISTAPPEND:
 	case ISN_LISTINDEX: