diff --git a/docs/_src/api/api/pipelines.md b/docs/_src/api/api/pipelines.md
index 6d9366d91..b9a5fa615 100644
--- a/docs/_src/api/api/pipelines.md
+++ b/docs/_src/api/api/pipelines.md
@@ -242,7 +242,7 @@ then be found in the dict returned by this method under the key "_debug"
 #### eval
 
 ```python
-def eval(labels: List[MultiLabel], documents: Optional[List[List[Document]]] = None, params: Optional[dict] = None, sas_model_name_or_path: str = None, add_isolated_node_eval: bool = False) -> EvaluationResult
+def eval(labels: List[MultiLabel], documents: Optional[List[Optional[List[Document]]]] = None, params: Optional[dict] = None, sas_model_name_or_path: str = None, add_isolated_node_eval: bool = False) -> EvaluationResult
 ```
 
 Evaluates the pipeline by running the pipeline once per query in debug mode
diff --git a/haystack/pipelines/base.py b/haystack/pipelines/base.py
index a02424c26..ca184c99a 100644
--- a/haystack/pipelines/base.py
+++ b/haystack/pipelines/base.py
@@ -480,7 +480,7 @@ class Pipeline(BasePipeline):
     def eval(
         self,
         labels: List[MultiLabel],
-        documents: Optional[List[List[Document]]] = None,
+        documents: Optional[List[Optional[List[Document]]]] = None,
         params: Optional[dict] = None,
         sas_model_name_or_path: str = None,
         add_isolated_node_eval: bool = False,