diff --git a/cotengra/interface.py b/cotengra/interface.py
index 45a288f..edb540c 100644
--- a/cotengra/interface.py
+++ b/cotengra/interface.py
@@ -661,6 +661,10 @@ def array_contract_expression(
     --------
     einsum_expression, array_contract, array_contract_tree
     """
+    inputs, output, size_dict = normalize_input(
+        inputs, output, size_dict, shapes, canonicalize=canonicalize
+    )
+
     if constants is not None:
         # handle constants specially with autoray
         return _array_contract_expression_with_constants(
@@ -673,10 +677,6 @@ def array_contract_expression(
             **kwargs,
         )
 
-    inputs, output, size_dict = normalize_input(
-        inputs, output, size_dict, shapes, canonicalize=canonicalize
-    )
-
     if cache and can_hash_optimize(optimize.__class__):
         try:
             key = hash_contraction(