diff --git a/pollination_dsl/alias/inputs.py b/pollination_dsl/alias/inputs.py
index 7c2badf..3253224 100644
--- a/pollination_dsl/alias/inputs.py
+++ b/pollination_dsl/alias/inputs.py
@@ -4,7 +4,7 @@
     DAGIntegerInputAlias, DAGNumberInputAlias, DAGBooleanInputAlias, \
     DAGJSONObjectInputAlias, DAGArrayInputAlias, DAGFileInputAlias, \
     DAGFolderInputAlias, DAGPathInputAlias, DAGLinkedInputAlias
-from queenbee.base.basemodel import BaseModel, Field
+from queenbee.base.basemodel import BaseModel, Field, validator
 from queenbee.io.common import ItemType, IOAliasHandler
 
 
@@ -39,11 +39,16 @@ class _InputAliasBase(BaseModel):
         'value can be any strings as long as it has been agreed between client-side '
         'developer and author of the recipe.'
     )
+
     handler: List[IOAliasHandler] = Field(
-        ...,
+        None,
         description='List of process actions to process the input or output value.'
     )
 
+    @validator('handler', always=True)
+    def create_empty_list(cls, v):
+        return [] if v is None else v
+
     @property
     def required(self):
         if self.optional:
diff --git a/pollination_dsl/alias/outputs.py b/pollination_dsl/alias/outputs.py
index 7a392ee..3698829 100644
--- a/pollination_dsl/alias/outputs.py
+++ b/pollination_dsl/alias/outputs.py
@@ -8,7 +8,7 @@
     DAGFileOutputAlias, DAGPathOutputAlias, DAGJSONObjectOutputAlias,
     DAGArrayOutputAlias, DAGLinkedOutputAlias
 )
-from queenbee.base.basemodel import BaseModel
+from queenbee.base.basemodel import BaseModel, validator
 from queenbee.io.common import ItemType, IOAliasHandler
 
 from pydantic import Field
@@ -59,10 +59,14 @@ class _OutputAliasBase(BaseModel):
     )
 
     handler: List[IOAliasHandler] = Field(
-        ...,
+        None,
         description='List of process actions to process the input or output value.'
     )
 
+    @validator('handler', always=True)
+    def create_empty_list(cls, v):
+        return [] if v is None else v
+
     @property
     def required(self):
         if self.optional: