diff --git a/python/taichi/lang/struct.py b/python/taichi/lang/struct.py
index 6e1ba512b16f4..b0ebc50f0f277 100644
--- a/python/taichi/lang/struct.py
+++ b/python/taichi/lang/struct.py
@@ -1,7 +1,7 @@
 import numbers
 from types import MethodType
 
-from taichi.lang import expr, impl, ops
+from taichi.lang import impl, ops
 from taichi.lang.common_ops import TaichiOperations
 from taichi.lang.enums import Layout
 from taichi.lang.exception import TaichiSyntaxError
@@ -648,21 +648,22 @@ def __init__(self, **kwargs):
                 self.members[k] = cook_dtype(dtype)
 
     def __call__(self, *args, **kwargs):
-        if len(args) == 0:
-            if kwargs == {}:
-                raise TaichiSyntaxError(
-                    "Custom type instances need to be created with an initial value."
-                )
-            else:
-                # initialize struct members by keywords
-                entries = Struct(kwargs)
-        elif len(args) == 1:
-            # fill a single scalar
-            if isinstance(args[0], (numbers.Number, expr.Expr)):
-                entries = self.filled_with_scalar(args[0])
+        d = {}
+        items = self.members.items()
+        for index, pair in enumerate(items):
+            name, dtype = pair
+            if isinstance(dtype, CompoundType):
+                if index < len(args):
+                    d[name] = dtype(args[index])
+                else:
+                    d[name] = kwargs.get(name, dtype(0))
             else:
-                # initialize struct members by dictionary
-                entries = Struct(args[0])
+                if index < len(args):
+                    d[name] = args[index]
+                else:
+                    d[name] = kwargs.get(name, 0)
+
+        entries = Struct(d)
         struct = self.cast(entries)
         return struct
 
diff --git a/tests/python/test_custom_struct.py b/tests/python/test_custom_struct.py
index 363148ece5716..260ddf7b21a8b 100644
--- a/tests/python/test_custom_struct.py
+++ b/tests/python/test_custom_struct.py
@@ -179,9 +179,9 @@ def run_python_scope():
 
     init_taichi_scope()
     for i in range(n):
-        assert x[i].idx == 1
+        assert x[i].idx == 0
         assert np.allclose(x[i].line.linedir.to_numpy(), 1.0)
-        assert x[i].line.length == 1.0
+        assert x[i].line.length == 0.0
     run_taichi_scope()
     for i in range(n):
         assert x[i].idx == i
@@ -189,9 +189,9 @@ def run_python_scope():
         assert x[i].line.length == i + 0.5
     init_python_scope()
     for i in range(n):
-        assert x[i].idx == 3
+        assert x[i].idx == 0
         assert np.allclose(x[i].line.linedir.to_numpy(), 3.0)
-        assert x[i].line.length == 3.0
+        assert x[i].line.length == 0.0
     run_python_scope()
     for i in range(n):
         assert x[i].idx == i
@@ -293,20 +293,20 @@ def test_compound_type_implicit_cast():
 
     @ti.kernel
     def f2i_taichi_scope() -> int:
-        s = structi(2.5)
+        s = structi(2.5, (2.5, 2.5))
         return s.a + s.b[0] + s.b[1]
 
     def f2i_python_scope():
-        s = structi(2.5)
+        s = structi(2.5, (2.5, 2.5))
         return s.a + s.b[0] + s.b[1]
 
     @ti.kernel
     def i2f_taichi_scope() -> float:
-        s = structf(2)
+        s = structf(2, (2, 2))
         return s.a + s.b[0] + s.b[1]
 
     def i2f_python_scope():
-        s = structf(2)
+        s = structf(2, (2, 2))
         return s.a + s.b[0] + s.b[1]
 
     int_value = f2i_taichi_scope()
@@ -396,3 +396,23 @@ def test():
         assert a.b == 3
 
     test()
+
+
+@test_utils.test(debug=True)
+def test_dataclass():
+    vec3 = ti.types.vector(3, float)
+
+    @ti.dataclass
+    class Foo:
+        pos: vec3
+        vel: vec3
+        mass: float
+
+    @ti.kernel
+    def test():
+        A = Foo((1, 1, 1), mass=2)
+        assert all(A.pos == [1.0, 1.0, 1.0])
+        assert all(A.vel == [0.0, 0.0, 0.0])
+        assert A.mass == 2.0
+
+    test()