diff --git a/pymc_extras/prior.py b/pymc_extras/prior.py
index a4f5ffa4..9693116e 100644
--- a/pymc_extras/prior.py
+++ b/pymc_extras/prior.py
@@ -97,7 +97,7 @@ def custom_transform(x):
 
 from pydantic import InstanceOf, validate_call
 from pydantic.dataclasses import dataclass
-from pymc.distributions.shape_utils import Dims
+from pymc.distributions.shape_utils import Dims, StrongDims
 
 from pymc_extras.deserialize import deserialize, register_deserialization
 
@@ -576,7 +576,7 @@ def __init__(
     ) -> None:
         self.distribution = distribution
         self.parameters = parameters
-        self.dims = dims
+        self.dims: StrongDims = dims
         self.centered = centered
         self.transform = transform
 
@@ -606,12 +606,16 @@ def transform(self, transform: str | None) -> None:
         self.pytensor_transform = not transform or _get_transform(transform)  # type: ignore
 
     @property
-    def dims(self) -> Dims:
-        """The dimensions of the variable."""
+    def dims(self) -> StrongDims:
+        """The dimensions of the variable.
+
+        It will always be a tuple. Empty tuple for scalar variables.
+
+        """
         return self._dims
 
     @dims.setter
-    def dims(self, dims) -> None:
+    def dims(self, dims: Dims | None) -> None:
         if isinstance(dims, str):
             dims = (dims,)