diff --git a/src/spox/_adapt.py b/src/spox/_adapt.py
index 8c95b2d..ff84817 100644
--- a/src/spox/_adapt.py
+++ b/src/spox/_adapt.py
@@ -9,10 +9,11 @@
 
 from ._attributes import AttrGraph
 from ._inline import _Inline
-from ._internal_op import _InternalNode
+from ._internal_op import _Initializer, _InternalNode
 from ._node import Node
 from ._schemas import SCHEMAS
 from ._scope import Scope
+from ._utils import from_array
 from ._var import VarInfo
 
 
@@ -30,16 +31,21 @@ def adapt_node(
         # By using a dictionary we ensure that we only have a single
         # ValueInfo per (possibly repeated) input name.
         input_info = {
-            var_names[var]: var.unwrap_type()._to_onnx_value_info(
-                var_names[var], _traceback_name=f"adapt-input {key}"
+            var_names[var_info]: var_info.unwrap_type()._to_onnx_value_info(
+                var_names[var_info], _traceback_name=f"adapt-input {key}"
             )
-            for key, var in node.inputs.get_var_infos().items()
+            for key, var_info in node.inputs.get_var_infos().items()
         }
         output_info = [
-            var.unwrap_type()._to_onnx_value_info(
-                var_names[var], _traceback_name=f"adapt-output {key}"
+            var_info.unwrap_type()._to_onnx_value_info(
+                var_names[var_info], _traceback_name=f"adapt-output {key}"
             )
-            for key, var in node.outputs.get_var_infos().items()
+            for key, var_info in node.outputs.get_var_infos().items()
+        ]
+        initializers = [
+            from_array(var_info._op.attrs.get_fields()["value"].value, name)  # type: ignore
+            for name, var_info in node.inputs.get_var_infos().items()
+            if isinstance(var_info._op, _Initializer)
         ]
     except ValueError:
         return None
@@ -50,6 +56,7 @@ def adapt_node(
             "spox__singleton_adapter_graph",
             list(input_info.values()),
             output_info,
+            initializers,
         ),
         opset_imports=[onnx.helper.make_operatorsetid("", source_version)],
     )
diff --git a/tests/test_adapt.py b/tests/test_adapt.py
index 25c4764..a90e077 100644
--- a/tests/test_adapt.py
+++ b/tests/test_adapt.py
@@ -15,6 +15,7 @@
 from spox import Tensor, Var, argument, build, inline
 from spox._attributes import AttrInt64s
 from spox._fields import BaseAttributes, BaseInputs, BaseOutputs
+from spox._future import initializer
 from spox._graph import arguments, results
 from spox._node import OpType
 from spox._standard import StandardNode
@@ -163,6 +164,18 @@ def test_adapt_node_with_repeating_input_names():
     build({"a": a}, {"b": b, "c": c})
 
 
+def test_adapt_node_initializer():
+    init_data = [1.0, 2.0, 3.0]
+
+    a = argument(Tensor(np.float32, ("N",)))
+    b = initializer(init_data, np.float32)
+    c = op18.equal(a, b)
+    d = op19.identity(a)
+
+    model = build({"a": a}, {"b": b, "c": c, "d": d})
+    np.testing.assert_allclose(model.graph.initializer[0].float_data, init_data)
+
+
 def test_inline_model_custom_node_only():
     """Inline a model which only consists of a custom node.