diff --git a/ergotree-ir/src/chain/json/sigma_protocol.rs b/ergotree-ir/src/chain/json/sigma_protocol.rs
index 6ce868185..0b87614b4 100644
--- a/ergotree-ir/src/chain/json/sigma_protocol.rs
+++ b/ergotree-ir/src/chain/json/sigma_protocol.rs
@@ -13,6 +13,8 @@ use crate::sigma_protocol::sigma_boolean::ProveDlog;
 use crate::sigma_protocol::sigma_boolean::SigmaBoolean;
 use crate::sigma_protocol::sigma_boolean::SigmaConjecture;
 use crate::sigma_protocol::sigma_boolean::SigmaProofOfKnowledgeTree;
+use alloc::string::String;
+use alloc::string::ToString;
 use alloc::vec::Vec;
 use bounded_vec::BoundedVecOutOfBounds;
 use ergo_chain_types::EcPoint;