diff --git a/Cargo.toml b/Cargo.toml
index fa918f7..f203b68 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ wee_alloc = { version = "0.4.4", optional = true }
 qimalloc = { version = "0.1", optional = true }
 
 [features]
-default = ["std", "wee_alloc"]
+default = ["wee_alloc"]
 std = []
 debug = []
 experimental = []
diff --git a/circle.yml b/circle.yml
index 6e8ab55..c644d3f 100644
--- a/circle.yml
+++ b/circle.yml
@@ -9,7 +9,8 @@ jobs:
       - run:
           name: Update rustc
           command: |
-            rustup target add wasm32-unknown-unknown
+            rustup install nightly-x86_64-unknown-linux-gnu
+            rustup target add wasm32-unknown-unknown --toolchain nightly
             rustup component add rustfmt
             rustup update
       - run:
@@ -20,28 +21,28 @@ jobs:
       - run:
           name: Test
           command: |
-             cargo test --target=x86_64-unknown-linux-gnu
-             cargo test --release --target=x86_64-unknown-linux-gnu
+             cargo +nightly test --target=x86_64-unknown-linux-gnu
+             cargo +nightly test --release --target=x86_64-unknown-linux-gnu
       - run:
           name: Build
           command: |
              # debug
-             cargo build
+             cargo +nightly build
              # release
-             cargo build --release
+             cargo +nightly build --release
              # different allocators
-             cargo build --release --features wee_alloc
-             cargo build --release --features qimalloc
+             cargo +nightly build --release --features wee_alloc
+             cargo +nightly build --release --features qimalloc
              # different allocators (no_std)
-             cargo build --release --no-default-features --features wee_alloc
-             cargo build --release --no-default-features --features qimalloc
+             cargo +nightly build --release --no-default-features --features wee_alloc
+             cargo +nightly build --release --no-default-features --features qimalloc
              # different feature sets
-             cargo build --release --no-default-features
-             cargo build --release --features debug
-             cargo build --release --no-default-features --features debug
-             cargo build --release --features experimental
-             cargo build --release --no-default-features --features experimental
-             cargo build --release --features experimental,debug
-             cargo build --release --no-default-features --features experimental,debug
-             cargo build --release --features eth2
-             cargo build --release --no-default-features --features eth2
+             cargo +nightly build --release --no-default-features
+             cargo +nightly build --release --features debug
+             cargo +nightly build --release --no-default-features --features debug
+             cargo +nightly build --release --features experimental
+             cargo +nightly build --release --no-default-features --features experimental
+             cargo +nightly build --release --features experimental,debug
+             cargo +nightly build --release --no-default-features --features experimental,debug
+             cargo +nightly build --release --features eth2
+             cargo +nightly build --release --no-default-features --features eth2
diff --git a/src/lib.rs b/src/lib.rs
index 9e7e48c..aa5ff9d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+#![feature(lang_items)]
+
 //! ewasm_api is a library used to interface with Ethereum's EEI in [Ewasm](https://github.com/ewasm/design), a set of enhancements to
 //! the Ethereum smart contract platform.
 //! ewasm_api exposes both a set of unsafe "native" functions representing the actual EEI
diff --git a/src/utils.rs b/src/utils.rs
index 6b3076c..d640078 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -15,6 +15,7 @@ pub fn unsafe_alloc_buffer(len: usize) -> Vec<u8> {
 mod tests {
     use super::*;
 
+    #[cfg(feature = "std")]
     #[test]
     fn smoke() {
         let ret = unsafe_alloc_buffer(42);