diff --git a/crates/starknet-types-rpc/src/custom_serde/num_as_hex.rs b/crates/starknet-types-rpc/src/custom_serde/num_as_hex.rs
index 6a90361..149d29d 100644
--- a/crates/starknet-types-rpc/src/custom_serde/num_as_hex.rs
+++ b/crates/starknet-types-rpc/src/custom_serde/num_as_hex.rs
@@ -1,3 +1,4 @@
+use alloc::vec::Vec;
 use core::marker::PhantomData;
 
 /// A trait for types that should be serialized or deserialized as hexadecimal strings.