diff --git a/src/diffusers/models/attention_processor.py b/src/diffusers/models/attention_processor.py
index 12a1eef34db2..55096d180ea2 100644
--- a/src/diffusers/models/attention_processor.py
+++ b/src/diffusers/models/attention_processor.py
@@ -103,7 +103,7 @@ def __init__(
         cross_attention_norm_num_groups: int = 32,
         qk_norm: Optional[str] = None,
         added_kv_proj_dim: Optional[int] = None,
-        added_proj_bias: Optional[bool] = None,
+        added_proj_bias: Optional[bool] = True,
         norm_num_groups: Optional[int] = None,
         spatial_norm_dim: Optional[int] = None,
         out_bias: bool = True,