diff --git a/bayesflow/simulators/composite_simulator.py b/bayesflow/simulators/composite_simulator.py
index f8c0eb4b..c6b7a5de 100644
--- a/bayesflow/simulators/composite_simulator.py
+++ b/bayesflow/simulators/composite_simulator.py
@@ -1,8 +1,8 @@
 from collections.abc import Sequence
 import numpy as np
 
-from bayesflow.types import Shape
-from bayesflow.utils import validate_batch_shape
+from bayesflow.types import ShapeLike
+from bayesflow.utils import validate_shape
 
 from .simulator import Simulator
 
@@ -14,8 +14,8 @@ def __init__(self, simulators: Sequence[Simulator], expand_outputs: bool = False
         self.simulators = simulators
         self.expand_outputs = expand_outputs
 
-    def sample(self, batch_shape: Shape, **kwargs) -> dict[str, np.ndarray]:
-        batch_shape = validate_batch_shape(batch_shape)
+    def sample(self, batch_shape: ShapeLike, **kwargs) -> dict[str, np.ndarray]:
+        batch_shape = validate_shape(batch_shape)
 
         data = {}
         for simulator in self.simulators:
diff --git a/bayesflow/simulators/hierarchical_simulator.py b/bayesflow/simulators/hierarchical_simulator.py
index 6657034c..fc53847e 100644
--- a/bayesflow/simulators/hierarchical_simulator.py
+++ b/bayesflow/simulators/hierarchical_simulator.py
@@ -2,18 +2,18 @@
 import keras
 import numpy as np
 
-from bayesflow.types import Shape
+from bayesflow.types import ShapeLike
 
 from .simulator import Simulator
-from bayesflow.utils import validate_batch_shape
+from bayesflow.utils import validate_shape
 
 
 class HierarchicalSimulator(Simulator):
     def __init__(self, hierarchy: Sequence[Simulator]):
         self.hierarchy = hierarchy
 
-    def sample(self, batch_shape: Shape, **kwargs) -> dict[str, np.ndarray]:
-        batch_shape = validate_batch_shape(batch_shape)
+    def sample(self, batch_shape: ShapeLike, **kwargs) -> dict[str, np.ndarray]:
+        batch_shape = validate_shape(batch_shape)
 
         input_data = {}
         output_data = {}
diff --git a/bayesflow/simulators/lambda_simulator.py b/bayesflow/simulators/lambda_simulator.py
index 3f919bbb..d762d635 100644
--- a/bayesflow/simulators/lambda_simulator.py
+++ b/bayesflow/simulators/lambda_simulator.py
@@ -4,8 +4,8 @@
 from bayesflow.utils import batched_call, filter_kwargs, tree_stack
 
 from .simulator import Simulator
-from bayesflow.utils import validate_batch_shape
-from ..types import Shape
+from bayesflow.utils import validate_shape
+from ..types import Shape, ShapeLike
 
 
 class LambdaSimulator(Simulator):
@@ -43,8 +43,9 @@ def __init__(
 
         self.reserved_arguments = reserved_arguments
 
-    def sample(self, batch_shape: Shape, **kwargs) -> dict[str, np.ndarray]:
-        batch_shape = validate_batch_shape(batch_shape)
+    def sample(self, batch_shape: ShapeLike, **kwargs) -> dict[str, np.ndarray]:
+        batch_shape = validate_shape(batch_shape)
+
         # add reserved arguments
         kwargs = self.reserved_arguments | kwargs
 
diff --git a/bayesflow/simulators/model_comparison_simulator.py b/bayesflow/simulators/model_comparison_simulator.py
index 8bc76998..9f5293de 100644
--- a/bayesflow/simulators/model_comparison_simulator.py
+++ b/bayesflow/simulators/model_comparison_simulator.py
@@ -1,13 +1,13 @@
 from collections.abc import Sequence
 import numpy as np
 
-from bayesflow.types import Shape
+from bayesflow.types import ShapeLike
 from bayesflow.utils import tree_stack
 
 from bayesflow.utils import numpy_utils as npu
 
 from .simulator import Simulator
-from bayesflow.utils import validate_batch_shape
+from bayesflow.utils import validate_shape
 
 
 class ModelComparisonSimulator(Simulator):
@@ -41,8 +41,8 @@ def __init__(
         self.logits = logits
         self.use_mixed_batches = use_mixed_batches
 
-    def sample(self, batch_shape: Shape, **kwargs) -> dict[str, np.ndarray]:
-        batch_shape = validate_batch_shape(batch_shape)
+    def sample(self, batch_shape: ShapeLike, **kwargs) -> dict[str, np.ndarray]:
+        batch_shape = validate_shape(batch_shape)
 
         if not self.use_mixed_batches:
             # draw one model index for the whole batch (faster)
diff --git a/bayesflow/simulators/simulator.py b/bayesflow/simulators/simulator.py
index f0fdddba..97d31d20 100644
--- a/bayesflow/simulators/simulator.py
+++ b/bayesflow/simulators/simulator.py
@@ -1,23 +1,25 @@
 from collections.abc import Callable
 import numpy as np
 
-from bayesflow.types import Shape
-from bayesflow.utils import tree_concatenate
+from bayesflow.types import ShapeLike
+from bayesflow.utils import tree_concatenate, validate_shape
 
 
 class Simulator:
-    def sample(self, batch_shape: Shape, **kwargs) -> dict[str, np.ndarray]:
+    def sample(self, batch_shape: ShapeLike, **kwargs) -> dict[str, np.ndarray]:
         raise NotImplementedError
 
     def rejection_sample(
         self,
-        batch_shape: Shape,
+        batch_shape: ShapeLike,
         predicate: Callable[[dict[str, np.ndarray]], np.ndarray],
         *,
         axis: int = 0,
         sample_size: int = None,
         **kwargs,
     ) -> dict[str, np.ndarray]:
+        batch_shape = validate_shape(batch_shape)
+
         if sample_size is None:
             sample_shape = batch_shape
         else:
diff --git a/bayesflow/types/__init__.py b/bayesflow/types/__init__.py
index 16253178..d954bae6 100644
--- a/bayesflow/types/__init__.py
+++ b/bayesflow/types/__init__.py
@@ -1,2 +1,2 @@
-from .shape import Shape
+from .shape import Shape, ShapeLike
 from .tensor import Tensor
diff --git a/bayesflow/types/shape.py b/bayesflow/types/shape.py
index 32b630b4..850cd512 100644
--- a/bayesflow/types/shape.py
+++ b/bayesflow/types/shape.py
@@ -1 +1,2 @@
-Shape = int | tuple[int, ...]
+Shape = tuple[int, ...]
+ShapeLike = int | Shape
diff --git a/bayesflow/utils/__init__.py b/bayesflow/utils/__init__.py
index fc1ec300..6cc822ea 100644
--- a/bayesflow/utils/__init__.py
+++ b/bayesflow/utils/__init__.py
@@ -36,7 +36,7 @@
 
 from .optimal_transport import optimal_transport
 
-from .validators import validate_batch_shape
+from .validators import validate_shape
 
 from .tensor_utils import (
     expand_left,
diff --git a/bayesflow/utils/validators.py b/bayesflow/utils/validators.py
index 54aab3d1..2a4b275d 100644
--- a/bayesflow/utils/validators.py
+++ b/bayesflow/utils/validators.py
@@ -1,8 +1,11 @@
-from bayesflow.types import Shape
+from bayesflow.types import Shape, ShapeLike
 
 
-def validate_batch_shape(batch_shape: Shape) -> tuple:
-    if isinstance(batch_shape, int):
-        batch_shape = (batch_shape,)
+def validate_shape(shape: ShapeLike) -> Shape:
+    if isinstance(shape, int):
+        return (shape,)
 
-    return batch_shape
+    if not isinstance(shape, tuple) or not all(isinstance(dim, int) for dim in shape):
+        raise ValueError(f"Invalid shape: {shape}")
+
+    return shape