diff --git a/ethcore/src/json_tests/executive.rs b/ethcore/src/json_tests/executive.rs
index 22a38f38797..86fa59bb2d8 100644
--- a/ethcore/src/json_tests/executive.rs
+++ b/ethcore/src/json_tests/executive.rs
@@ -300,7 +300,7 @@ fn do_json_test_for<H: FnMut(&str, HookType)>(vm_type: &VMType, json_data: &[u8]
 				&mut tracer,
 				&mut vm_tracer,
 			));
-			let mut evm = vm_factory.create(params, &schedule, 0).expect("Current tests are all of version 0; factory always return Some; qed");
+			let evm = vm_factory.create(params, &schedule, 0).expect("Current tests are all of version 0; factory always return Some; qed");
 			let res = evm.exec(&mut ex).ok().expect("TestExt never trap; resume error never happens; qed");
 			// a return in finalize will not alter callcreates
 			let callcreates = ex.callcreates.clone();
diff --git a/ethcore/src/lib.rs b/ethcore/src/lib.rs
index e7aa7385647..c36e5ec7afa 100644
--- a/ethcore/src/lib.rs
+++ b/ethcore/src/lib.rs
@@ -96,6 +96,7 @@ extern crate rayon;
 extern crate rlp;
 extern crate parity_util_mem;
 extern crate parity_util_mem as malloc_size_of;
+#[cfg(any(test, feature = "test-helpers"))]
 extern crate rustc_hex;
 extern crate serde;
 extern crate state_db;
diff --git a/ethcore/src/miner/miner.rs b/ethcore/src/miner/miner.rs
index ad6ecaae8c2..efa67219320 100644
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@@ -1107,7 +1107,7 @@ impl miner::MinerService for Miner {
 						Eq(value) => tx_value == value,
 						GreaterThan(value) => tx_value > value,
 						LessThan(value) => tx_value < value,
-						// Will always occure on `Any`, other operators
+						// Will always occur on `Any`, other operators
 						// get handled during deserialization
 						_ => true,
 					}
@@ -1123,7 +1123,7 @@ impl miner::MinerService for Miner {
 							let sender = tx.signed().sender();
 							match filter.from {
 								Eq(value) => sender == value,
-								// Will always occure on `Any`, other operators
+								// Will always occur on `Any`, other operators
 								// get handled during deserialization
 								_ => true,
 							}
@@ -1136,7 +1136,7 @@ impl miner::MinerService for Miner {
 							match filter.to {
 								// Could apply to `Some(Address)` or `None` (for contract creation)
 								Eq(value) => receiver == value,
-								// Will always occure on `Any`, other operators
+								// Will always occur on `Any`, other operators
 								// get handled during deserialization
 								_ => true,
 							}
diff --git a/ethcore/wasm/src/runtime.rs b/ethcore/wasm/src/runtime.rs
index d7690e26ab1..34030d308d7 100644
--- a/ethcore/wasm/src/runtime.rs
+++ b/ethcore/wasm/src/runtime.rs
@@ -128,7 +128,7 @@ impl ::std::fmt::Display for Error {
 			Error::AllocationFailed => write!(f, "Memory allocation failed (OOM)"),
 			Error::BadUtf8 => write!(f, "String encoding is bad utf-8 sequence"),
 			Error::GasLimit => write!(f, "Invocation resulted in gas limit violated"),
-			Error::Log => write!(f, "Error occured while logging an event"),
+			Error::Log => write!(f, "Error occurred while logging an event"),
 			Error::InvalidSyscall => write!(f, "Invalid syscall signature encountered at runtime"),
 			Error::Other => write!(f, "Other unspecified error"),
 			Error::Unreachable => write!(f, "Unreachable instruction encountered"),