diff --git a/fixed-hash/src/hash.rs b/fixed-hash/src/hash.rs
index ea2210076..09ce43d8c 100644
--- a/fixed-hash/src/hash.rs
+++ b/fixed-hash/src/hash.rs
@@ -107,19 +107,19 @@ macro_rules! construct_fixed_hash {
 		impl $name {
 			/// Returns a new fixed hash where all bits are set to the given byte.
 			#[inline]
-			pub fn repeat_byte(byte: u8) -> $name {
+			pub const fn repeat_byte(byte: u8) -> $name {
 				$name([byte; $n_bytes])
 			}
 
 			/// Returns a new zero-initialized fixed hash.
 			#[inline]
-			pub fn zero() -> $name {
+			pub const fn zero() -> $name {
 				$name::repeat_byte(0u8)
 			}
 
 			/// Returns the size of this hash in bytes.
 			#[inline]
-			pub fn len_bytes() -> usize {
+			pub const fn len_bytes() -> usize {
 				$n_bytes
 			}
 
@@ -137,7 +137,7 @@ macro_rules! construct_fixed_hash {
 
 			/// Extracts a reference to the byte array containing the entire fixed hash.
 			#[inline]
-			pub fn as_fixed_bytes(&self) -> &[u8; $n_bytes] {
+			pub const fn as_fixed_bytes(&self) -> &[u8; $n_bytes] {
 				&self.0
 			}
 
@@ -149,7 +149,7 @@ macro_rules! construct_fixed_hash {
 
 			/// Returns the inner bytes array.
 			#[inline]
-			pub fn to_fixed_bytes(self) -> [u8; $n_bytes] {
+			pub const fn to_fixed_bytes(self) -> [u8; $n_bytes] {
 				self.0
 			}
 
diff --git a/rlp/src/rlpin.rs b/rlp/src/rlpin.rs
index f1c488626..6cdfaa808 100644
--- a/rlp/src/rlpin.rs
+++ b/rlp/src/rlpin.rs
@@ -25,7 +25,7 @@ struct OffsetCache {
 }
 
 impl OffsetCache {
-	fn new(index: usize, offset: usize) -> OffsetCache {
+	const fn new(index: usize, offset: usize) -> OffsetCache {
 		OffsetCache { index, offset }
 	}
 }
@@ -68,7 +68,7 @@ fn calculate_payload_info(header_bytes: &[u8], len_of_len: usize) -> Result<Payl
 }
 
 impl PayloadInfo {
-	fn new(header_len: usize, value_len: usize) -> PayloadInfo {
+	const fn new(header_len: usize, value_len: usize) -> PayloadInfo {
 		PayloadInfo { header_len, value_len }
 	}
 
@@ -128,7 +128,7 @@ impl<'a> fmt::Display for Rlp<'a> {
 }
 
 impl<'a> Rlp<'a> {
-	pub fn new(bytes: &'a [u8]) -> Rlp<'a> {
+	pub const fn new(bytes: &'a [u8]) -> Rlp<'a> {
 		Rlp { bytes, offset_cache: Cell::new(None), count_cache: Cell::new(None) }
 	}
 
@@ -374,7 +374,7 @@ pub struct BasicDecoder<'a> {
 }
 
 impl<'a> BasicDecoder<'a> {
-	pub fn new(rlp: &'a [u8]) -> BasicDecoder<'a> {
+	pub const fn new(rlp: &'a [u8]) -> BasicDecoder<'a> {
 		BasicDecoder { rlp }
 	}
 
diff --git a/uint/src/uint.rs b/uint/src/uint.rs
index b15726b72..7dd1bca42 100644
--- a/uint/src/uint.rs
+++ b/uint/src/uint.rs
@@ -371,7 +371,7 @@ macro_rules! construct_uint {
 			impl $name {
 				/// Low 2 words (u128)
 				#[inline]
-				pub fn low_u128(&self) -> u128 {
+				pub const fn low_u128(&self) -> u128 {
 					let &$name(ref arr) = self;
 					((arr[1] as u128) << 64) + arr[0] as u128
 				}
@@ -473,14 +473,14 @@ macro_rules! construct_uint {
 
 			/// Conversion to u32
 			#[inline]
-			pub fn low_u32(&self) -> u32 {
+			pub const fn low_u32(&self) -> u32 {
 				let &$name(ref arr) = self;
 				arr[0] as u32
 			}
 
 			/// Low word (u64)
 			#[inline]
-			pub fn low_u64(&self) -> u64 {
+			pub const fn low_u64(&self) -> u64 {
 				let &$name(ref arr) = self;
 				arr[0]
 			}
@@ -560,7 +560,7 @@ macro_rules! construct_uint {
 			///
 			/// Panics if `index` exceeds the bit width of the number.
 			#[inline]
-			pub fn bit(&self, index: usize) -> bool {
+			pub const fn bit(&self, index: usize) -> bool {
 				let &$name(ref arr) = self;
 				arr[index / 64] & (1 << (index % 64)) != 0
 			}
@@ -601,7 +601,7 @@ macro_rules! construct_uint {
 			///
 			/// Panics if `index` exceeds the byte width of the number.
 			#[inline]
-			pub fn byte(&self, index: usize) -> u8 {
+			pub const fn byte(&self, index: usize) -> u8 {
 				let &$name(ref arr) = self;
 				(arr[index / 8] >> (((index % 8)) * 8)) as u8
 			}
@@ -1066,18 +1066,18 @@ macro_rules! construct_uint {
 			}
 
 			#[inline(always)]
-			fn mul_u64(a: u64, b: u64, carry: u64) -> (u64, u64) {
-				let (hi, lo) = Self::split_u128(u128::from(a) * u128::from(b) + u128::from(carry));
+			const fn mul_u64(a: u64, b: u64, carry: u64) -> (u64, u64) {
+				let (hi, lo) = Self::split_u128(a as u128 * b as u128 + carry as u128);
 				(lo, hi)
 			}
 
 			#[inline(always)]
-			fn split(a: u64) -> (u64, u64) {
+			const fn split(a: u64) -> (u64, u64) {
 				(a >> 32, a & 0xFFFF_FFFF)
 			}
 
 			#[inline(always)]
-			fn split_u128(a: u128) -> (u64, u64) {
+			const fn split_u128(a: u128) -> (u64, u64) {
 				((a >> 64) as _, (a & 0xFFFFFFFFFFFFFFFF) as _)
 			}