diff --git a/concrete/numpy/representation/evaluator.py b/concrete/numpy/representation/evaluator.py
new file mode 100644
index 000000000..56470e3fa
--- /dev/null
+++ b/concrete/numpy/representation/evaluator.py
@@ -0,0 +1,50 @@
+"""
+Declaration of various `Evaluator` classes, to make graphs picklable.
+"""
+
+
+class ConstantEvaluator:
+    """
+    ConstantEvaluator class, to evaluate Operation.Constant nodes.
+    """
+
+    def __init__(self, properties):
+        self.properties = properties
+
+    def __call__(self, *args, **kwargs):
+        return self.properties["constant"]
+
+
+class InputEvaluator:
+    """
+    InputEvaluator class, to evaluate Operation.Input nodes.
+    """
+
+    def __call__(self, *args, **kwargs):
+        return args[0]
+
+
+class GenericEvaluator:
+    """
+    GenericEvaluator class, to evaluate Operation.Generic nodes.
+    """
+
+    def __init__(self, operation, properties):
+        self.operation = operation
+        self.properties = properties
+
+    def __call__(self, *args, **kwargs):
+        return self.operation(*args, *self.properties["args"], **self.properties["kwargs"])
+
+
+class GenericTupleEvaluator:
+    """
+    GenericEvaluator class, to evaluate Operation.Generic nodes where args are packed in a tuple.
+    """
+
+    def __init__(self, operation, properties):
+        self.operation = operation
+        self.properties = properties
+
+    def __call__(self, *args, **kwargs):
+        return self.operation(tuple(args), *self.properties["args"], **self.properties["kwargs"])
diff --git a/concrete/numpy/representation/node.py b/concrete/numpy/representation/node.py
index 00c4172a0..5d796bfef 100644
--- a/concrete/numpy/representation/node.py
+++ b/concrete/numpy/representation/node.py
@@ -9,6 +9,7 @@ import numpy as np
 
 from ..internal.utils import assert_that
 from ..values import Value
+from .evaluator import ConstantEvaluator, GenericEvaluator, GenericTupleEvaluator, InputEvaluator
 from .operation import Operation
 from .utils import KWARGS_IGNORED_IN_FORMATTING, format_constant, format_indexing_element
 
@@ -50,7 +51,7 @@ class Node:
             raise ValueError(f"Constant {repr(constant)} is not supported") from error
 
         properties = {"constant": np.array(constant)}
-        return Node([], value, Operation.Constant, lambda: properties["constant"], properties)
+        return Node([], value, Operation.Constant, ConstantEvaluator(properties), properties)
 
     @staticmethod
     def generic(
@@ -99,17 +100,17 @@ class Node:
             "attributes": attributes if attributes is not None else {},
         }
 
-        if name == "concatenate":
-
-            def evaluator(*args):
-                return operation(tuple(args), *properties["args"], **properties["kwargs"])
-
-        else:
-
-            def evaluator(*args):
-                return operation(*args, *properties["args"], **properties["kwargs"])
-
-        return Node(inputs, output, Operation.Generic, evaluator, properties)
+        return Node(
+            inputs,
+            output,
+            Operation.Generic,
+            (
+                GenericTupleEvaluator(operation, properties)  # type: ignore
+                if name in ["concatenate"]
+                else GenericEvaluator(operation, properties)  # type: ignore
+            ),
+            properties,
+        )
 
     @staticmethod
     def input(name: str, value: Value) -> "Node":
@@ -128,7 +129,7 @@ class Node:
                 node representing input
         """
 
-        return Node([value], value, Operation.Input, lambda x: x, {"name": name})
+        return Node([value], value, Operation.Input, InputEvaluator(), {"name": name})
 
     def __init__(
         self,