diff --git a/substrate/Cargo.lock b/substrate/Cargo.lock
index 2d02a1799c..d0eee3e39a 100644
--- a/substrate/Cargo.lock
+++ b/substrate/Cargo.lock
@@ -170,6 +170,10 @@ dependencies = [
  "regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "environmental"
+version = "0.1.0"
+
 [[package]]
 name = "error-chain"
 version = "0.11.0"
@@ -833,8 +837,10 @@ dependencies = [
 name = "runtime-support"
 version = "0.1.0"
 dependencies = [
+ "environmental 0.1.0",
  "lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "polkadot-state-machine 0.1.0",
 ]
 
 [[package]]
diff --git a/substrate/Cargo.toml b/substrate/Cargo.toml
index bfbff56969..21232d39ef 100644
--- a/substrate/Cargo.toml
+++ b/substrate/Cargo.toml
@@ -12,6 +12,7 @@ members = [
 	"candidate-agreement",
 	"client",
 	"collator",
+	"environmental",
 	"executor",
 	"primitives",
 	"rpc",
diff --git a/substrate/environmental/src/lib.rs b/substrate/environmental/src/lib.rs
index db46b13158..420c22f44f 100644
--- a/substrate/environmental/src/lib.rs
+++ b/substrate/environmental/src/lib.rs
@@ -27,20 +27,23 @@ pub fn using_environment<'a, T: 'a, S, F: FnOnce()>(
 	global.with(|r| *r.borrow_mut() = 0 as *mut S);
 }
 
-pub fn with_environment<'r, S, T: 'r, F: FnOnce(&'r mut T)>(
+pub fn with_environment<'r, R, S, T: 'r, F: FnOnce(&'r mut T) -> R>(
 	global: &'static LocalKey<RefCell<*mut S>>,
 	mutator: F,
-) {
+) -> Option<R> {
+
 	global.with(|r| {
 		let br = r.borrow_mut();
 		if *br != 0 as *mut S {
 			// safe because it's only non-zero when it in with_environment, which
 			// is holding on to the underlying reference safely
 			unsafe {
-				mutator(&mut *(*br as *mut S as *mut T));
+				Some(mutator(&mut *(*br as *mut S as *mut T)))
 			}
+		} else {
+			None
 		}
-	});
+	})
 }
 
 #[macro_export]
@@ -64,16 +67,18 @@ macro_rules! declare_generic_environment {
 				$crate::using_environment(&GLOBAL, protected, f);
 			}
 
-			pub fn with<F: for<'r, 't: 'r> FnOnce(&'r mut $t<'t>)>(f: F) {
+			pub fn with<R, F: for<'r, 't: 'r> FnOnce(&'r mut $t<'t>) -> R>(
+				f: F
+			) -> Option<R> {
 				let dummy = ();
-				with_closed(f, &dummy);
+				with_closed(f, &dummy)
 			}
 
-			fn with_closed<'d: 't, 't: 'r, 'r, F: FnOnce(&'r mut $t<'t>)>(
+			fn with_closed<'d: 't, 't: 'r, 'r, R, F: FnOnce(&'r mut $t<'t>) -> R>(
 				f: F,
 				_dummy: &'d (),
-			) {
-				$crate::with_environment(&GLOBAL, f);
+			) -> Option<R> {
+				$crate::with_environment(&GLOBAL, f)
 			}
 		}
 	}
@@ -91,16 +96,18 @@ macro_rules! declare_simple_environment {
 				$crate::using_environment(&GLOBAL, protected, f);
 			}
 
-			pub fn with<F: for<'r> FnOnce(&'r mut $t)>(f: F) {
+			pub fn with<R, F: for<'r> FnOnce(&'r mut $t -> R)>(
+				f: F
+			) -> Option<R> {
 				let dummy = ();
-				with_closed(f, &dummy);
+				with_closed(f, &dummy)
 			}
 
-			fn with_closed<'d: 'r, 'r, F: FnOnce(&'r mut $t)>(
+			fn with_closed<'d: 'r, 'r, R, F: FnOnce(&'r mut $t -> R)>(
 				f: F,
 				_dummy: &'d (),
-			) {
-				$crate::with_environment(&GLOBAL, f);
+			) -> Option<R> {
+				$crate::with_environment(&GLOBAL, f)
 			}
 		}
 	}
diff --git a/substrate/executor/src/wasm_utils.rs b/substrate/executor/src/wasm_utils.rs
index 6d4fedfedb..f6440628b9 100644
--- a/substrate/executor/src/wasm_utils.rs
+++ b/substrate/executor/src/wasm_utils.rs
@@ -119,13 +119,13 @@ pub trait IntoUserDefinedElements {
 #[macro_export]
 macro_rules! impl_function_executor {
 	( $objectname:ident : $structname:ty, $( $name:ident ( $( $names:ident : $params:ty ),* ) $( -> $returns:ty )* => $body:tt ),* => $($pre:tt)+ ) => (
-		impl $( $pre ) + $crate::wasm_utils::UserFunctionExecutor<$crate::wasm_utils::DummyUserError> for $structname {
+		impl $($pre)+ $crate::wasm_utils::UserFunctionExecutor<$crate::wasm_utils::DummyUserError> for $structname {
 			dispatch!($objectname, $( $name( $( $names : $params ),* ) $( -> $returns )* => $body ),*);
 		}
-		impl $( $pre ) + $structname {
+		impl $($pre)+ $structname {
 			signatures!($( $name( $( $params ),* ) $( -> $returns )* ),*);
 		}
-		impl $( $pre ) + $crate::wasm_utils::IntoUserDefinedElements for $structname {
+		impl $($pre)+ $crate::wasm_utils::IntoUserDefinedElements for $structname {
 			fn into_user_defined_elements(&mut self) -> UserDefinedElements<$crate::wasm_utils::DummyUserError> {
 				$crate::wasm_utils::UserDefinedElements {
 					executor: Some(self),
diff --git a/substrate/native-runtime/support/Cargo.toml b/substrate/native-runtime/support/Cargo.toml
index 4f4e0202b5..3f979bd4ff 100644
--- a/substrate/native-runtime/support/Cargo.toml
+++ b/substrate/native-runtime/support/Cargo.toml
@@ -9,3 +9,5 @@ strict = []
 [dependencies]
 lazy_static = "1.0.0"
 parking_lot = "0.5"
+polkadot-state-machine = { path = "../../state_machine" , version = "0.1" }
+environmental = { path = "../../environmental", version = "0.1.0" }
diff --git a/substrate/native-runtime/support/src/lib.rs b/substrate/native-runtime/support/src/lib.rs
index 0e12d5e678..091e07fbce 100644
--- a/substrate/native-runtime/support/src/lib.rs
+++ b/substrate/native-runtime/support/src/lib.rs
@@ -1,6 +1,6 @@
 #[macro_use]
-extern crate lazy_static;
-extern crate parking_lot;
+extern crate environmental;
+extern crate polkadot_state_machine;
 
 pub use std::vec::Vec;
 pub use std::rc::Rc;
@@ -8,38 +8,51 @@ pub use std::cell::RefCell;
 pub use std::boxed::Box;
 pub use std::mem::{size_of, transmute};
 
-use std::collections::HashMap;
-use parking_lot::Mutex;
+use polkadot_state_machine::Externalities;
+use std::fmt;
 
-lazy_static! {
-	static ref HASHMAP: Mutex<HashMap<Vec<u8>, Vec<u8>>> = Mutex::new(HashMap::new());
+// TODO: use the real error, not NoError.
+
+#[derive(Debug)]
+struct NoError;
+impl fmt::Display for NoError {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "") }
 }
 
+pub struct ExternalitiesHolder<'a> {
+	ext: &'a mut Externalities<Error=NoError>,
+}
+
+declare_generic_environment!(ext : ExternalitiesHolder);
+
 pub fn storage(_key: &[u8]) -> Vec<u8> {
-	HASHMAP.lock().get(_key).cloned().unwrap_or_else(Vec::new)
+	ext::with(|holder| holder.ext.storage(_key).ok().map(|s| s.to_vec()))
+		.unwrap_or(None)
+		.unwrap_or_else(|| vec![])
 }
 
 pub fn storage_into<T: Sized>(_key: &[u8]) -> Option<T> {
 	let size = size_of::<T>();
-	if let Some(value) = HASHMAP.lock().get(_key) {
-		if value.len() == size {
-			unsafe {
-				let mut result: T = std::mem::uninitialized();
-				std::slice::from_raw_parts_mut(transmute::<*mut T, *mut u8>(&mut result), size)
-					.copy_from_slice(&value);
-				return Some(result);
+
+	ext::with(|holder| {
+		if let Ok(value) = holder.ext.storage(_key) {
+			if value.len() == size {
+				unsafe {
+					let mut result: T = std::mem::uninitialized();
+					std::slice::from_raw_parts_mut(transmute::<*mut T, *mut u8>(&mut result), size)
+						.copy_from_slice(&value);
+					return Some(result);
+				}
 			}
 		}
-	}
-	None
+		None
+	}).unwrap_or(None)
 }
 
 pub fn set_storage(_key: &[u8], _value: &[u8]) {
-	HASHMAP.lock().insert(_key.to_vec(), _value.to_vec());
-}
-
-pub fn init_storage(new: HashMap<Vec<u8>, Vec<u8>>) {
-	*HASHMAP.lock() = new;
+	ext::with(|holder|
+		holder.ext.set_storage(_key.to_vec(), _value.to_vec())
+	);
 }
 
 #[macro_export]
@@ -50,6 +63,23 @@ macro_rules! impl_stubs {
 #[cfg(test)]
 mod tests {
 	use super::*;
+	use std::collections::HashMap;
+
+	#[derive(Debug, Default)]
+	struct TestExternalities {
+		storage: HashMap<Vec<u8>, Vec<u8>>,
+	}
+	impl Externalities for TestExternalities {
+		type Error = NoError;
+
+		fn storage(&self, key: &[u8]) -> Result<&[u8], NoError> {
+			Ok(self.storage.get(&key.to_vec()).map_or(&[] as &[u8], Vec::as_slice))
+		}
+
+		fn set_storage(&mut self, key: Vec<u8>, value: Vec<u8>) {
+			self.storage.insert(key, value);
+		}
+	}
 
 	macro_rules! map {
 		($( $name:expr => $value:expr ),*) => (
@@ -59,15 +89,29 @@ mod tests {
 
 	#[test]
 	fn storage_works() {
-		assert_eq!(storage(b"hello"), vec![]);
-		set_storage(b"hello", b"world");
-		assert_eq!(storage(b"hello"), b"world".to_vec());
-		assert_eq!(storage(b"foo"), vec![]);
-		set_storage(b"foo", &[1, 2, 3][..]);
-		assert_eq!(storage_into::<[u8; 3]>(b"foo"), Some([1, 2, 3]));
-		assert_eq!(storage_into::<[u8; 3]>(b"hello"), None);
-		init_storage(map![b"foo".to_vec() => b"bar".to_vec()]);
-		assert_eq!(storage(b"hello"), vec![]);
-		assert_eq!(storage(b"foo"), b"bar".to_vec());
+		let mut t = TestExternalities { storage: map![], };
+
+		{
+			let mut h = ExternalitiesHolder { ext: &mut t, };
+			ext::using(&mut h, || {
+				assert_eq!(storage(b"hello"), b"".to_vec());
+				set_storage(b"hello", b"world");
+				assert_eq!(storage(b"hello"), b"world".to_vec());
+				assert_eq!(storage(b"foo"), b"".to_vec());
+				set_storage(b"foo", &[1, 2, 3][..]);
+				assert_eq!(storage_into::<[u8; 3]>(b"foo"), Some([1, 2, 3]));
+				assert_eq!(storage_into::<[u8; 3]>(b"hello"), None);
+			});
+		}
+
+		t.storage = map![b"foo".to_vec() => b"bar".to_vec()];
+
+		{
+			let mut h = ExternalitiesHolder { ext: &mut t, };
+			ext::using(&mut h, || {
+				assert_eq!(storage(b"hello"), b"".to_vec());
+				assert_eq!(storage(b"foo"), b"bar".to_vec());
+			});
+		}
 	}
 }