diff --git a/src/api.rs b/src/api.rs
index 2c8cf32..12cfef0 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -1499,13 +1499,6 @@ pub fn evaluate_state(init_commitment: String, previous_state: Option<String>, s
 }
 
 fn add_validation_token(init_commitment: String, merkle_root_hex: String, approval: bool) -> ApiResult<ApiReturn> {
-    let mut merkle_root = [0u8; 32];
-    let pcd_commitment_vec = Vec::from_hex(&merkle_root_hex)?;
-    if pcd_commitment_vec.len() != 32 {
-        return Err(ApiError::new("pcd_commitment must be 32B long".to_owned()));
-    }
-    merkle_root.copy_from_slice(&pcd_commitment_vec);
-
     let mut processes = lock_processes()?;
 
     let outpoint = OutPoint::from_str(&init_commitment)?;
@@ -1513,29 +1506,30 @@ fn add_validation_token(init_commitment: String, merkle_root_hex: String, approv
     let process = processes.get_mut(&outpoint)
         .ok_or(ApiError::new("Unknown process".to_owned()))?;
 
-    let update_state: &mut ProcessState = process.get_state_for_commitments_root(merkle_root)?;
+    {
+        let update_state: &mut ProcessState = process.get_state_for_commitments_root_mut(&merkle_root_hex)?;
 
-    let message_hash = if approval {
-        AnkHash::ValidationYes(AnkValidationYesHash::from_byte_array(merkle_root))
-    } else {
-        AnkHash::ValidationNo(AnkValidationNoHash::from_byte_array(merkle_root))
-    };
+        let mut merkle_root = [0u8; 32];
 
-    let local_device = lock_local_device()?;
-    let sp_wallet = local_device.get_wallet();
-    let proof = Proof::new(message_hash, sp_wallet.get_client().get_spend_key().try_into()?);
+        merkle_root.copy_from_slice(&Vec::from_hex(&merkle_root_hex)?);
 
-    // we copy the state before modifying it
-    let previous_state = update_state.clone();
+        let message_hash = if approval {
+            AnkHash::ValidationYes(AnkValidationYesHash::from_merkle_root(merkle_root))
+        } else {
+            AnkHash::ValidationNo(AnkValidationNoHash::from_merkle_root(merkle_root))
+        };
 
-    update_state.validation_tokens.push(proof);
+        let local_device = lock_local_device()?;
+        let sp_wallet = local_device.get_wallet();
+        let proof = Proof::new(message_hash, sp_wallet.get_client().get_spend_key().try_into()?);
 
-    let new_state = update_state.clone();
+        update_state.validation_tokens.push(proof);
+    }
 
     let updated_process = UpdatedProcess {
         commitment_tx: OutPoint::from_str(&init_commitment)?,
         current_process: process.clone(),
-        modified_state: Some((previous_state, new_state)),
+        modified_state: Some(merkle_root_hex),
         ..Default::default()
     };