diff --git a/brainunit/_base.py b/brainunit/_base.py
index c29b40d..b56d7e3 100644
--- a/brainunit/_base.py
+++ b/brainunit/_base.py
@@ -4502,30 +4502,24 @@ def new_f(*args, **kwds):
                     newkeyset[n] = v
 
             result = f(**newkeyset)
-            if isinstance(result, tuple):
-                assert isinstance(au["result"], tuple), "The return value of the function is a tuple, but the decorator expected a single unit."
-                result = tuple(
-                    Quantity(r, unit=au["result"][i]) if isinstance(au["result"][i], Unit) else r
-                    for i, r in enumerate(result)
-                )
             if "result" in au:
-                specific_unit = au["result"]
-                if specific_unit == bool:
-                    if isinstance(result, bool):
-                        pass
-                    else:
-                        raise TypeError(f"Function '{f.__name__}' expected a boolean value for the return value but got '{result}'")
-                elif specific_unit == 1:
-                    if isinstance(result, Quantity):
-                        result = result.to_decimal()
-                    elif isinstance(result, (jax.Array, np.ndarray, int, float, complex)):
-                        result = jnp.asarray(result)
-                    else:
-                        specific_unit = jax.typing.ArrayLike
-                        raise TypeError(f"Function '{f.__name__}' expected a unitless Quantity object"
-                                        f" or {specific_unit} for the return value but got '{result}'")
-                elif isinstance(specific_unit, Unit):
-                    result = Quantity(result, unit=specific_unit)
+                if isinstance(au["result"], Callable) and au["result"] != bool:
+                    expected_result = au["result"](*[get_unit(a) for a in args])
+                else:
+                    expected_result = au["result"]
+
+                if (
+                    jax.tree.structure(expected_result, is_leaf=_is_quantity)
+                    !=
+                    jax.tree.structure(result, is_leaf=_is_quantity)
+                ):
+                    raise TypeError(
+                        f"Expected a return value of type {expected_result} but got {result}"
+                    )
+
+                result = jax.tree.map(
+                    partial(_assign_unit, f), result, expected_result
+                )
             return result
 
         return new_f
@@ -4543,6 +4537,11 @@ def _check_unit(f, val, unit):
         )
         raise UnitMismatchError(error_message, get_unit(val))
 
+def _assign_unit(f, val, unit):
+    if unit is None or unit == bool or unit == 1:
+        return val
+    return Quantity(val, unit=unit)
+
 
 def _is_quantity(x):
     return isinstance(x, Quantity)
diff --git a/brainunit/_base_test.py b/brainunit/_base_test.py
index 5cd9053..b66d996 100644
--- a/brainunit/_base_test.py
+++ b/brainunit/_base_test.py
@@ -1427,7 +1427,7 @@ def b_function():
             Return a value in seconds if return_second is True, otherwise return
             a value in volt.
             """
-            return 5 * second
+            return 5
 
         # Should work (returns second)
         assert b_function() == 5 * second