diff --git a/modelx/core/system.py b/modelx/core/system.py
index 08a3fd5..0bda294 100644
--- a/modelx/core/system.py
+++ b/modelx/core/system.py
@@ -51,7 +51,7 @@ def eval_node(self, node):
         cells = node[OBJ]
         key = node[KEY]
 
-        if cells.has_node(key):
+        if cells.is_cached and cells.has_node(key):
             value = cells.data[key]
             if self.callstack:
                 # Shortcut for append & pop for performance
diff --git a/modelx/tests/core/cells/test_cache.py b/modelx/tests/core/cells/test_cache.py
index a8687c7..c681cf6 100644
--- a/modelx/tests/core/cells/test_cache.py
+++ b/modelx/tests/core/cells/test_cache.py
@@ -77,3 +77,25 @@ def bar(x):
     assert foo(3) == 12
 
     m.close()
+
+
+def test_unhashable_arg():
+
+    m = mx.new_model()
+
+    @mx.defcells
+    def foo(x):
+        return bar([1, 2, 3])
+
+    @mx.defcells
+    def bar(l: list):
+        return l
+
+    bar.is_cached = False
+
+    foo(0)
+
+    assert foo.preds(0)[0].obj is bar
+    assert foo.preds(0)[0].args is None
+
+    m.close()