diff --git a/zero/src/prover.rs b/zero/src/prover.rs
index 794c61878..70772210b 100644
--- a/zero/src/prover.rs
+++ b/zero/src/prover.rs
@@ -31,7 +31,6 @@ use crate::ops;
 //
 // While proving a block interval, we will output proofs corresponding to block
 // batches as soon as they are generated.
-const DEFAULT_PARALLEL_BLOCK_PROVING_PERMIT_POOL_SIZE: usize = 16;
 static PARALLEL_BLOCK_PROVING_PERMIT_POOL: Semaphore = Semaphore::const_new(0);
 
 #[derive(Debug, Clone)]
@@ -247,7 +246,7 @@ pub async fn prove(
         PARALLEL_BLOCK_PROVING_PERMIT_POOL.add_permits(prover_config.block_pool_size);
     } else {
         anyhow::bail!(
-            "block_pool_size should be greater than 0, value passed from cli is {}",
+            "block_pool_size should be greater than 0, cli parameter value is {}",
             prover_config.block_pool_size
         );
     }
diff --git a/zero/src/prover/cli.rs b/zero/src/prover/cli.rs
index 94ca03ed4..a6cdaebf9 100644
--- a/zero/src/prover/cli.rs
+++ b/zero/src/prover/cli.rs
@@ -43,7 +43,8 @@ pub struct CliProverConfig {
     /// generate one proof file.
     #[arg(long, default_value_t = 8)]
     block_batch_size: usize,
-    /// The maximum number of block proving tasks that can run in parallel.
+    /// The maximum number of block proving tasks that can run in parallel. Must
+    /// be greater than zero.
     #[arg(long, default_value_t = 16)]
     block_pool_size: usize,
 }