diff --git a/Cargo.lock b/Cargo.lock
index 3e88b40cb..79217f7e2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -256,7 +256,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "crunchy"
-version = "0.1.0"
+version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -365,7 +365,7 @@ dependencies = [
 name = "ethash"
 version = "1.7.0"
 dependencies = [
- "crunchy 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crunchy 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "primal 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2949,7 +2949,7 @@ dependencies = [
 "checksum core-foundation 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "20a6d0448d3a99d977ae4a2aa5a98d886a923e863e81ad9ff814645b6feb3bbd"
 "checksum core-foundation-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "05eed248dc504a5391c63794fe4fb64f46f071280afaa1b73308f3c0ce4574c5"
 "checksum crossbeam 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)" = "0c5ea215664ca264da8a9d9c3be80d2eaf30923c259d03e870388eb927508f97"
-"checksum crunchy 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b56bdac907d4b64254aed43964b11dd334bc46e0826a0e3add75caddfaf90175"
+"checksum crunchy 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "803315676d3fc09db67636977586262e7d1a6c5bdb291810efd5ceb48a0d5d58"
 "checksum crypt32-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e34988f7e069e0b2f3bfc064295161e489b2d4e04a2e4248fb94360cdf00b4ec"
 "checksum ctrlc 1.1.1 (git+https://github.com/paritytech/rust-ctrlc.git)" = "<none>"
 "checksum daemonize 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "271ec51b7e0bee92f0d04601422c73eb76ececf197026711c97ad25038a010cf"
diff --git a/ethash/src/compute.rs b/ethash/src/compute.rs
index 67b1ea678..21dd0a7c7 100644
--- a/ethash/src/compute.rs
+++ b/ethash/src/compute.rs
@@ -298,7 +298,7 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 
 				let index = fnv_hash(
 					f_mix.get_unchecked(0).as_words().get_unchecked(0) ^ i,
-					*mix.get_unchecked(0).as_words().get_unchecked(i_usize % MIX_WORDS)
+					*mix.get_unchecked(0).as_words().get_unchecked(i as usize % MIX_WORDS)
 				) % num_full_pages;
 
 				unroll! {
@@ -324,14 +324,18 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 			}
 		}
 
+		debug_assert_eq!(MIX_WORDS / 4, 8);
+
 		// compress mix
-		for i in 0..(MIX_WORDS / 4) {
-			let w = i * 4;
-			let mut reduction = *mix.get_unchecked(0).as_words().get_unchecked(w + 0);
-			reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 1);
-			reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 2);
-			reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 3);
-			*mix.get_unchecked_mut(0).as_words_mut().get_unchecked_mut(i) = reduction;
+		unroll! {
+			for i in 0..8 {
+				let w = i * 4;
+				let mut reduction = *mix.get_unchecked(0).as_words().get_unchecked(w + 0);
+				reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 1);
+				reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 2);
+				reduction = reduction.wrapping_mul(FNV_PRIME) ^ *mix.get_unchecked(0).as_words().get_unchecked(w + 3);
+				*mix.get_unchecked_mut(0).as_words_mut().get_unchecked_mut(i) = reduction;
+			}
 		}
 
 		let mut mix_hash = [0u8; 32];
@@ -356,13 +360,15 @@ fn calculate_dag_item(node_index: u32, cache: &[Node]) -> Node {
 		*ret.as_words_mut().get_unchecked_mut(0) ^= node_index;
 		sha3::sha3_512(ret.bytes.as_mut_ptr(), ret.bytes.len(), ret.bytes.as_ptr(), ret.bytes.len());
 
-		for i in 0..ETHASH_DATASET_PARENTS {
+		for i_usize in 0..ETHASH_DATASET_PARENTS {
+			let i = i_usize as u32;
 			let parent_index = fnv_hash(node_index ^ i, *ret.as_words().get_unchecked(i as usize % NODE_WORDS)) % num_parent_nodes as u32;
 			let parent = cache.get_unchecked(parent_index as usize);
 			for w in 0..NODE_WORDS {
 				*ret.as_words_mut().get_unchecked_mut(w) = fnv_hash(*ret.as_words().get_unchecked(w), *parent.as_words().get_unchecked(w));
 			}
 		}
+
 		sha3::sha3_512(ret.bytes.as_mut_ptr(), ret.bytes.len(), ret.bytes.as_ptr(), ret.bytes.len());
 		ret
 	}
@@ -386,6 +392,7 @@ fn light_new(block_number: u64) -> Light {
 			sha3::sha3_512(nodes.get_unchecked_mut(i).bytes.as_mut_ptr(), NODE_BYTES, nodes.get_unchecked(i - 1).bytes.as_ptr(), NODE_BYTES);
 		}
 
+		// This _should_ get unrolled by the compiler, since it's not using the loop variable.
 		for _ in 0..ETHASH_CACHE_ROUNDS {
 			for i in 0..num_nodes {
 				let idx = *nodes.get_unchecked_mut(i).as_words().get_unchecked(0) as usize % num_nodes;