diff --git a/Cargo.toml b/Cargo.toml
index 7538eee..459043f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,2 +1,2 @@
 [workspace]
-members = ["uint", "fixed-hash", "ethereum-types", "tests", "ethbloom"]
+members = ["uint", "fixed-hash", "ethereum-types", "tests", "ethbloom"]
\ No newline at end of file
diff --git a/ethbloom/Cargo.toml b/ethbloom/Cargo.toml
index 4d8b01d..8c525bf 100644
--- a/ethbloom/Cargo.toml
+++ b/ethbloom/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ethbloom"
-version = "0.4.0"
+version = "0.4.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 description = "Ethereum bloom filter"
 license = "MIT"
diff --git a/ethbloom/src/lib.rs b/ethbloom/src/lib.rs
index 6fb99e3..6150da8 100644
--- a/ethbloom/src/lib.rs
+++ b/ethbloom/src/lib.rs
@@ -28,8 +28,6 @@
 
 #![cfg_attr(not(feature="std"), no_std)]
 
-#![cfg_attr(asm_available, feature(asm))]
-
 #[cfg(feature="std")]
 extern crate core;
 
diff --git a/ethereum-types/Cargo.toml b/ethereum-types/Cargo.toml
index 33ea15d..0ca5b3f 100644
--- a/ethereum-types/Cargo.toml
+++ b/ethereum-types/Cargo.toml
@@ -1,10 +1,11 @@
 [package]
 name = "ethereum-types"
-version = "0.2.0"
+version = "0.2.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 homepage = "https://github.com/paritytech/primitives"
 description = "Ethereum types"
+build = "build.rs"
 
 [build-dependencies]
 rustc_version = "0.2"
@@ -22,3 +23,4 @@ default = ["std", "heapsizeof", "serialize"]
 std = ["uint/std", "fixed-hash/std", "ethbloom/std"]
 heapsizeof = ["uint/heapsizeof", "fixed-hash/heapsizeof", "ethbloom/heapsizeof"]
 serialize = ["std", "ethereum-types-serialize", "serde", "ethbloom/serialize"]
+use_asm = ["uint/use_asm"]
\ No newline at end of file
diff --git a/ethereum-types/build.rs b/ethereum-types/build.rs
index 432acc3..3ba1687 100644
--- a/ethereum-types/build.rs
+++ b/ethereum-types/build.rs
@@ -11,7 +11,9 @@ extern crate rustc_version;
 use rustc_version::{version_meta, Channel};
 
 fn main() {
-	if let Channel::Nightly = version_meta().unwrap().channel {
-		println!("cargo:rustc-cfg=asm_available");
+	if cfg!(feature = "use_asm") { 
+		if let Channel::Nightly = version_meta().unwrap().channel {
+			println!("cargo:rustc-cfg=asm_available");
+		}
 	}
 }
diff --git a/ethereum-types/src/lib.rs b/ethereum-types/src/lib.rs
index 55fdeec..85452f3 100644
--- a/ethereum-types/src/lib.rs
+++ b/ethereum-types/src/lib.rs
@@ -28,4 +28,4 @@ pub use fixed_hash::clean_0x;
 pub type Address = H160;
 pub type Secret = H256;
 pub type Public = H512;
-pub type Signature = H520;
+pub type Signature = H520;
\ No newline at end of file
diff --git a/tests/Cargo.toml b/tests/Cargo.toml
index e7b2b21..e466302 100644
--- a/tests/Cargo.toml
+++ b/tests/Cargo.toml
@@ -11,3 +11,6 @@ crunchy = "0.1.5"
 ethereum-types = { path ="../ethereum-types", features = ["std", "heapsizeof"] }
 quickcheck = "0.6"
 uint = { path = "../uint" }
+
+[features]
+use_asm = ["uint/use_asm", "ethereum-types/use_asm"]
\ No newline at end of file
diff --git a/tests/build.rs b/tests/build.rs
deleted file mode 100644
index 432acc3..0000000
--- a/tests/build.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright 2015-2017 Parity Technologies
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-extern crate rustc_version;
-
-use rustc_version::{version_meta, Channel};
-
-fn main() {
-	if let Channel::Nightly = version_meta().unwrap().channel {
-		println!("cargo:rustc-cfg=asm_available");
-	}
-}
diff --git a/tests/src/lib.rs b/tests/src/lib.rs
index 342dbef..1ceb036 100644
--- a/tests/src/lib.rs
+++ b/tests/src/lib.rs
@@ -1,5 +1,3 @@
-#![cfg_attr(asm_available, feature(asm))]
-
 extern crate core;
 #[cfg(test)]
 #[macro_use]
@@ -13,4 +11,4 @@ extern crate crunchy;
 extern crate quickcheck;
 
 #[cfg(test)]
-pub mod uint_tests;
+pub mod uint_tests;
\ No newline at end of file
diff --git a/uint/Cargo.toml b/uint/Cargo.toml
index c37a00c..8433f2a 100644
--- a/uint/Cargo.toml
+++ b/uint/Cargo.toml
@@ -4,7 +4,7 @@ homepage = "http://parity.io"
 repository = "https://github.com/paritytech/primitives"
 license = "MIT/Apache-2.0"
 name = "uint"
-version = "0.1.0"
+version = "0.1.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 build = "build.rs"
 
@@ -22,6 +22,7 @@ crunchy = "0.1.5"
 [features]
 std = ["rustc-hex"]
 heapsizeof = ["heapsize"]
+use_asm = []
 
 [[example]]
 name = "modular"
diff --git a/uint/build.rs b/uint/build.rs
index 432acc3..3ba1687 100644
--- a/uint/build.rs
+++ b/uint/build.rs
@@ -11,7 +11,9 @@ extern crate rustc_version;
 use rustc_version::{version_meta, Channel};
 
 fn main() {
-	if let Channel::Nightly = version_meta().unwrap().channel {
-		println!("cargo:rustc-cfg=asm_available");
+	if cfg!(feature = "use_asm") { 
+		if let Channel::Nightly = version_meta().unwrap().channel {
+			println!("cargo:rustc-cfg=asm_available");
+		}
 	}
 }