diff --git a/src/snakia/core/rx/__init__.py b/src/snakia/core/rx/__init__.py
index d411a45..b4bf207 100644
--- a/src/snakia/core/rx/__init__.py
+++ b/src/snakia/core/rx/__init__.py
@@ -2,7 +2,7 @@ from .async_bindable import AsyncBindable
 from .base_bindable import BaseBindable, BindableSubscriber, ValueChanged
 from .bindable import Bindable
 from .chains import chain
-from .combines import combine
+from .combines import async_combine, combine
 from .concats import concat
 from .conds import cond
 from .consts import const
@@ -16,6 +16,8 @@ __all__ = [
     "BaseBindable",
     "BindableSubscriber",
     "ValueChanged",
+    "async_combine",
+    "async_merge",
     "chain",
     "combine",
     "concat",
@@ -24,5 +26,4 @@ __all__ = [
     "filter",
     "map",
     "merge",
-    "async_merge",
 ]
diff --git a/src/snakia/core/rx/combines.py b/src/snakia/core/rx/combines.py
index 7b519bd..345d0a7 100644
--- a/src/snakia/core/rx/combines.py
+++ b/src/snakia/core/rx/combines.py
@@ -1,12 +1,11 @@
-import operator
-from typing import Any, Callable, TypeVar, overload
+from typing import Any, Awaitable, Callable, TypeVar, overload
 
-from snakia.utils import to_async
+from snakia.types import Unset
+from snakia.utils import caller, to_async
 
 from .async_bindable import AsyncBindable
 from .base_bindable import ValueChanged
 from .bindable import Bindable
-from .concats import concat
 
 A = TypeVar("A")
 B = TypeVar("B")
@@ -22,6 +21,7 @@ def combine(
     /,
     *,
     combiner: Callable[[A], R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
@@ -32,6 +32,7 @@ def combine(
     /,
     *,
     combiner: Callable[[A, B], R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
@@ -43,6 +44,7 @@ def combine(
     /,
     *,
     combiner: Callable[[A, B, C], R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
@@ -55,6 +57,7 @@ def combine(
     /,
     *,
     combiner: Callable[[A, B, C, D], R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
@@ -67,6 +70,7 @@ def combine(
     /,
     *,
     combiner: Callable[[A, B, C, D], R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
@@ -74,28 +78,116 @@ def combine(
 def combine(
     *sources: Bindable[Any] | AsyncBindable[Any],
     combiner: Callable[..., R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]: ...
 
 
 def combine(
     *sources: Bindable[Any] | AsyncBindable[Any],
     combiner: Callable[..., R],
+    default_value: R | Unset = Unset(),
 ) -> Bindable[R]:
     combined = Bindable[R]()
-    values = [*map(lambda s: s.value, sources)]
+    Unset.map(
+        default_value,
+        combined.set_silent,
+        caller(combined.set_silent, sources[0].default_value),
+    )
 
-    for i, source in enumerate(sources):
-
-        def make_subscriber(
-            index: int,
-        ) -> Callable[[ValueChanged[Any]], None]:
-            return concat(
-                lambda v: operator.setitem(values, index, v.new_value),
-                lambda _: combiner(*values),
-            )
+    def subscriber(_: ValueChanged[Any]) -> None:
+        combined.set(combiner(*[*map(lambda s: s.value, sources)]))
 
+    for source in sources:
         if isinstance(source, Bindable):
-            source.subscribe(make_subscriber(i))
+            source.subscribe(subscriber)
         else:
-            source.subscribe(to_async(make_subscriber(i)))
+            source.subscribe(to_async(subscriber))
+    return combined
+
+
+@overload
+def async_combine(
+    source1: AsyncBindable[A],
+    /,
+    *,
+    combiner: Callable[[A], Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+@overload
+def async_combine(
+    source1: AsyncBindable[A],
+    source2: AsyncBindable[B],
+    /,
+    *,
+    combiner: Callable[[A, B], Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+@overload
+def async_combine(
+    source1: AsyncBindable[A],
+    source2: AsyncBindable[B],
+    source3: AsyncBindable[C],
+    /,
+    *,
+    combiner: Callable[[A, B, C], Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+@overload
+def async_combine(
+    source1: AsyncBindable[A],
+    source2: AsyncBindable[B],
+    source3: AsyncBindable[C],
+    source4: AsyncBindable[D],
+    /,
+    *,
+    combiner: Callable[[A, B, C, D], Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+@overload
+def async_combine(
+    source1: AsyncBindable[A],
+    source2: AsyncBindable[B],
+    source3: AsyncBindable[C],
+    source4: AsyncBindable[D],
+    /,
+    *,
+    combiner: Callable[[A, B, C, D], Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+@overload
+def async_combine(
+    *sources: AsyncBindable[Any],
+    combiner: Callable[..., Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]: ...
+
+
+def async_combine(
+    *sources: AsyncBindable[Any],
+    combiner: Callable[..., Awaitable[R]],
+    default_value: R | Unset = Unset(),
+) -> AsyncBindable[R]:
+    combined = AsyncBindable[R]()
+    Unset.map(
+        default_value,
+        combined.set_silent,
+        caller(combined.set_silent, sources[0].default_value),
+    )
+
+    async def subscriber(_: ValueChanged[Any]) -> None:
+        result = await combiner(*[*map(lambda s: s.value, sources)])
+        await combined.set(result)
+
+    for source in sources:
+        source.subscribe(subscriber)
     return combined