diff --git a/crates/prover/src/core/backend/simd/grind.rs b/crates/prover/src/core/backend/simd/grind.rs
index 22d197f420..8e8837cbba 100644
--- a/crates/prover/src/core/backend/simd/grind.rs
+++ b/crates/prover/src/core/backend/simd/grind.rs
@@ -126,7 +126,7 @@ fn grind_poseidon31(digest: &[M31; 8], hi: u64, pow_bits: u32) -> Option<u64> {
             M31::from_u32_unchecked((((start + i as u64) >> 43) & ((1 << 21) - 1)) as u32)
         }));
 
-        let res = permute(attempt)[8];
+        let res = permute(attempt)[0];
         let success_mask = res.into_simd().trailing_zeros().simd_ge(pow_bits);
         if success_mask.any() {
             let i = success_mask.to_array().iter().position(|&x| x).unwrap();
diff --git a/crates/prover/src/core/channel/poseidon31.rs b/crates/prover/src/core/channel/poseidon31.rs
index c9b718d446..be4b6cf3f6 100644
--- a/crates/prover/src/core/channel/poseidon31.rs
+++ b/crates/prover/src/core/channel/poseidon31.rs
@@ -112,7 +112,7 @@ impl Channel for Poseidon31Channel {
             poseidon2_permute(&mut state);
         }
 
-        let new_digest = state.last_chunk::<8>().unwrap();
+        let new_digest = state.first_chunk::<8>().unwrap();
         self.update_digest(*new_digest);
     }
 
@@ -142,7 +142,7 @@ impl Channel for Poseidon31Channel {
         ];
         poseidon2_permute(&mut state);
 
-        let new_digest = state.last_chunk::<8>().unwrap();
+        let new_digest = state.first_chunk::<8>().unwrap();
         self.update_digest(*new_digest);
     }