diff --git a/onnxruntime/core/graph/function_utils.cc b/onnxruntime/core/graph/function_utils.cc
index 9eaa3097fd..de7cec2b5d 100644
--- a/onnxruntime/core/graph/function_utils.cc
+++ b/onnxruntime/core/graph/function_utils.cc
@@ -123,6 +123,12 @@ static void IOTypeConstraintHelper(const ONNX_NAMESPACE::FunctionProto& onnx_fun
     const auto* node_op_schema = schema_registry->GetSchema(node.op_type(), domain_version, node.domain());
     int variadic_arg_idx = -1;
     for (int i = 0; i < node.input_size(); ++i) {
+      if (node_op_schema && variadic_arg_idx == -1) {
+        // The check is applied only if we have not seen a variadic parameter so far:
+        ORT_ENFORCE(static_cast<size_t>(i) < node_op_schema->inputs().size(),
+                    "Too many inputs for op " + node.op_type());
+      }
+
       auto& in_name = node.input().Get(i);
       auto iter = input_name_idx_map.find(in_name);
       if (iter != input_name_idx_map.end()) {
@@ -157,12 +163,12 @@ static void IOTypeConstraintHelper(const ONNX_NAMESPACE::FunctionProto& onnx_fun
             }
           }
         }
+      }
 
-        // if this is a variadic input there are no more inputs in the schema
-        if (node_op_schema && variadic_arg_idx == -1 &&
-            node_op_schema->inputs().at(schema_idx).GetOption() == OpSchema::FormalParameterOption::Variadic) {
-          variadic_arg_idx = i;
-        }
+      // if this is a variadic input there are no more inputs in the schema
+      if (node_op_schema && variadic_arg_idx == -1 &&
+          node_op_schema->inputs().at(i).GetOption() == OpSchema::FormalParameterOption::Variadic) {
+        variadic_arg_idx = i;
       }
     }
 
@@ -202,12 +208,12 @@ static void IOTypeConstraintHelper(const ONNX_NAMESPACE::FunctionProto& onnx_fun
             }
           }
         }
+      }
 
-        // if this is a variadic output there are no more outputs in the schema
-        if (node_op_schema && variadic_arg_idx == -1 &&
-            node_op_schema->outputs().at(schema_idx).GetOption() == OpSchema::FormalParameterOption::Variadic) {
-          variadic_arg_idx = i;
-        }
+      // if this is a variadic output there are no more outputs in the schema
+      if (node_op_schema && variadic_arg_idx == -1 &&
+          node_op_schema->outputs().at(i).GetOption() == OpSchema::FormalParameterOption::Variadic) {
+        variadic_arg_idx = i;
       }
     }
 
diff --git a/onnxruntime/test/framework/function_test.cc b/onnxruntime/test/framework/function_test.cc
index 21bd301a25..2979bb8767 100644
--- a/onnxruntime/test/framework/function_test.cc
+++ b/onnxruntime/test/framework/function_test.cc
@@ -353,6 +353,26 @@ TEST(FunctionTest, Variadics) {
   ASSERT_STATUS_OK(session_object.Initialize());
 }
 
+// A variation of the variadics issue above, where the first input/output of the
+// variadic list is NOT an input/output of the function.
+TEST(FunctionTest, VariadicsNonInputOutput) {
+  const char* code = R"(
+    <ir_version: 8, opset_import: ["" : 17, "local" : 1]>
+    mymodel (float[2] x) => (float[3] y) {
+      y = local.func (x)
+    }
+
+    <opset_import: ["" : 17 ],  domain: "local">
+    func (a) => (y) {
+      b = Identity(a)
+      z = Concat <axis = 0> (b, a, b)
+      y, w = Split (z)
+    }
+  )";
+
+  Check(code, "x", {1.0, 2.0}, "y", {1.0, 2.0, 1.0});
+}
+
 // Test use of outer-scope names inside sub-graphs in functions that are inlined.
 TEST(FunctionTest, OuterScopeName) {
   const char* code = R"(