diff --git a/beavers/engine.py b/beavers/engine.py
index 5aeb2e2..527e096 100644
--- a/beavers/engine.py
+++ b/beavers/engine.py
@@ -181,7 +181,7 @@ def input_nodes(self) -> typing.Tuple[Node]:
         return self.nodes
 
 
-NO_INPUTS = _NodeInputs.create([], {})
+_NO_INPUTS = _NodeInputs.create([], {})
 
 
 @dataclasses.dataclass
@@ -193,7 +193,7 @@ class _RuntimeNodeData(typing.Generic[T]):
     cycle_id: int
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, eq=False)
 class Node(typing.Generic[T]):
     """
     Represent an element in a `Dag`.
@@ -219,7 +219,7 @@ class Node(typing.Generic[T]):
     def _create(
         value: T = None,
         function: typing.Optional[typing.Callable[[...], T]] = None,
-        inputs: _NodeInputs = NO_INPUTS,
+        inputs: _NodeInputs = _NO_INPUTS,
         empty: typing.Any = _STATE_EMPTY,
         notifications: int = 1,
     ) -> Node:
@@ -354,7 +354,7 @@ def const(self, value: T) -> Node[T]:
         return self._add_node(
             Node._create(
                 function=_unchanged_callback,
-                inputs=NO_INPUTS,
+                inputs=_NO_INPUTS,
                 value=value,
                 notifications=0,
             )
@@ -386,7 +386,7 @@ def source_stream(
             node = self._add_stream(
                 function=_SourceStreamFunction(empty, name),
                 empty=empty,
-                inputs=NO_INPUTS,
+                inputs=_NO_INPUTS,
             )
             if name:
                 self._sources[name] = node
@@ -476,7 +476,7 @@ def timer_manager(self) -> Node[TimerManager]:
             Node._create(
                 value=function.timer_manager,
                 function=function,
-                inputs=NO_INPUTS,
+                inputs=_NO_INPUTS,
                 notifications=1,
             )
         )
diff --git a/tests/test_engine.py b/tests/test_engine.py
index 678ee31..1ac4bce 100644
--- a/tests/test_engine.py
+++ b/tests/test_engine.py
@@ -1,4 +1,5 @@
 import asyncio
+import operator
 import time
 
 import pandas as pd
@@ -574,5 +575,21 @@ def test_recalculate_clean_node():
         node._recalculate(2)
 
 
+def test_can_add_node_copy():
+    dag = Dag()
+    source = dag.source_stream([])
+    node_one = dag.stream(operator.__add__).map(source, source)
+    node_two = dag.stream(operator.__add__).map(source, source)
+    assert node_one is not node_two
+    assert node_one != node_two
+
+
+def test_can_not_add_node_back():
+    dag = Dag()
+    source = dag.source_stream([])
+    with pytest.raises(ValueError, match="Node already in dag"):
+        dag._add_node(source)
+
+
 def test_unchanged_callback():
     assert _unchanged_callback() is _STATE_UNCHANGED