diff --git a/keras/models/functional.py b/keras/models/functional.py
index e4732aff6cb4..d42ea29a1317 100644
--- a/keras/models/functional.py
+++ b/keras/models/functional.py
@@ -553,6 +553,10 @@ def process_layer(layer_data):
     def get_tensor(layer_name, node_index, tensor_index):
         assert layer_name in created_layers
         layer = created_layers[layer_name]
+        if issubclass(layer.__class__, Functional):
+            # Functional models start with a pre-existing node
+            # linking their input to output.
+            node_index -= 1
         layer_output_tensors = layer._inbound_nodes[node_index].output_tensors
         return layer_output_tensors[tensor_index]