diff --git a/transformer_lens/components/abstract_attention.py b/transformer_lens/components/abstract_attention.py
index 470c21231..8cd51ea91 100644
--- a/transformer_lens/components/abstract_attention.py
+++ b/transformer_lens/components/abstract_attention.py
@@ -600,7 +600,7 @@ def calculate_sin_cos_rotary(
         self,
         rotary_dim: int,
         n_ctx: int,
-        base: int = 10000,
+        base: Union[float, int] = 10000,
         dtype: torch.dtype = torch.float32,
     ) -> Tuple[Float[torch.Tensor, "n_ctx rotary_dim"], Float[torch.Tensor, "n_ctx rotary_dim"]]:
         """
diff --git a/transformer_lens/config/HookedTransformerConfig.py b/transformer_lens/config/HookedTransformerConfig.py
index 6b3d58bb9..e8450df1f 100644
--- a/transformer_lens/config/HookedTransformerConfig.py
+++ b/transformer_lens/config/HookedTransformerConfig.py
@@ -206,7 +206,7 @@ class HookedTransformerConfig(TransformerLensConfig):
             YARN extension. Defaults to 4096.
         use_qk_norm (bool): Whether to apply RMSNorm to the query and key projections before
             computing attention scores. Used by Gemma 3 models. Defaults to False.
-        rotary_base_local (int, *optional*): The base for rotary positional embeddings in local
+        rotary_base_local (float, *optional*): The base for rotary positional embeddings in local
             attention layers. Used by models with hybrid local/global attention (e.g., Gemma 3)
             which use different RoPE bases for local (10k) and global (1M) attention. Defaults
             to None, which means the standard rotary_base is used for all layers.
@@ -250,9 +250,9 @@ class HookedTransformerConfig(TransformerLensConfig):
     dtype: torch.dtype = torch.float32
     tokenizer_prepends_bos: Optional[bool] = None
     post_embedding_ln: bool = False
-    rotary_base: int = 10000
+    rotary_base: Union[float, int] = 10000
     rotary_base_local: Optional[
-        int
+        Union[float, int]
     ] = None  # For models with different RoPE bases per attention type (e.g., Gemma 3)
     rotary_scaling_factor: float = (
         1.0  # Linear RoPE scaling factor for global attention (e.g., 8.0 for Gemma 3 4B)