diff --git a/substrate/executor/src/wasm_executor.rs b/substrate/executor/src/wasm_executor.rs
index 2269de51d4..8a70271c1a 100644
--- a/substrate/executor/src/wasm_executor.rs
+++ b/substrate/executor/src/wasm_executor.rs
@@ -78,13 +78,18 @@ impl WritePrimitive<u32> for MemoryInstance {
 }
 
 impl_function_executor!(this: FunctionExecutor<'e, E>,
-	ext_print(utf8_data: *const u8, utf8_len: u32) => {
+	ext_print_utf8(utf8_data: *const u8, utf8_len: u32) => {
 		if let Ok(utf8) = this.memory.get(utf8_data, utf8_len as usize) {
 			if let Ok(message) = String::from_utf8(utf8) {
 				println!("Runtime: {}", message);
 			}
 		}
 	},
+	ext_print_hex(data: *const u8, len: u32) => {
+		if let Ok(hex) = this.memory.get(data, len as usize) {
+			println!("Runtime: {}", HexDisplay::from(&hex));
+		}
+	},
 	ext_print_num(number: u64) => {
 		println!("Runtime: {}", number);
 	},
diff --git a/substrate/native-runtime/support/src/lib.rs b/substrate/native-runtime/support/src/lib.rs
index 4d665fc0de..fb74093d18 100644
--- a/substrate/native-runtime/support/src/lib.rs
+++ b/substrate/native-runtime/support/src/lib.rs
@@ -40,6 +40,7 @@ pub mod prelude {
 }
 
 pub use polkadot_state_machine::{Externalities, ExternalitiesError};
+use primitives::hexdisplay::HexDisplay;
 
 // TODO: use the real error, not NoError.
 
@@ -111,9 +112,13 @@ pub trait Printable {
 
 impl<'a> Printable for &'a [u8] {
 	fn print(self) {
-		if let Ok(s) = ::std::str::from_utf8(self) {
-			println!("Runtime: {}", s);
-		}
+		println!("Runtime: {}", HexDisplay::from(&self));
+	}
+}
+
+impl<'a> Printable for &'a str {
+	fn print(self) {
+		println!("Runtime: {}", self);
 	}
 }
 
diff --git a/substrate/primitives/src/hexdisplay.rs b/substrate/primitives/src/hexdisplay.rs
index d6299a2e41..fa62d69869 100644
--- a/substrate/primitives/src/hexdisplay.rs
+++ b/substrate/primitives/src/hexdisplay.rs
@@ -39,6 +39,10 @@ pub trait AsBytesRef {
 	fn as_bytes_ref(&self) -> &[u8];
 }
 
+impl<'a> AsBytesRef for &'a [u8] {
+	fn as_bytes_ref(&self) -> &[u8] { self }
+}
+
 impl AsBytesRef for [u8] {
 	fn as_bytes_ref(&self) -> &[u8] { &self }
 }
diff --git a/substrate/wasm-runtime/polkadot/src/runtime/system.rs b/substrate/wasm-runtime/polkadot/src/runtime/system.rs
index 2749c3ad9f..b3d4640e78 100644
--- a/substrate/wasm-runtime/polkadot/src/runtime/system.rs
+++ b/substrate/wasm-runtime/polkadot/src/runtime/system.rs
@@ -85,7 +85,6 @@ pub fn execute_block(mut block: Block) {
 
 /// Execute a given transaction.
 pub fn execute_transaction(utx: &UncheckedTransaction) {
-	print(&b"HERE"[..]);
 	// Verify the signature is good.
 	assert!(utx.ed25519_verify(), "All transactions should be properly signed");
 
diff --git a/substrate/wasm-runtime/support/src/lib.rs b/substrate/wasm-runtime/support/src/lib.rs
index 454ba8507f..d506e193cd 100644
--- a/substrate/wasm-runtime/support/src/lib.rs
+++ b/substrate/wasm-runtime/support/src/lib.rs
@@ -28,7 +28,7 @@ extern crate pwasm_alloc;
 #[no_mangle]
 pub extern fn panic_fmt(_fmt: ::core::fmt::Arguments, _file: &'static str, _line: u32, _col: u32) {
 	unsafe {
-		ext_print(_file.as_ptr() as *const u8, _file.len() as u32);
+		ext_print_utf8(_file.as_ptr() as *const u8, _file.len() as u32);
 		ext_print_num(_line as u64);
 		ext_print_num(_col as u64);
 		::core::intrinsics::abort()
@@ -36,7 +36,8 @@ pub extern fn panic_fmt(_fmt: ::core::fmt::Arguments, _file: &'static str, _line
 }
 
 extern "C" {
-	fn ext_print(utf8_data: *const u8, utf8_len: u32);
+	fn ext_print_utf8(utf8_data: *const u8, utf8_len: u32);
+	fn ext_print_hex(data: *const u8, len: u32);
 	fn ext_print_num(value: u64);
 	fn ext_set_storage(key_data: *const u8, key_len: u32, value_data: *const u8, value_len: u32);
 	fn ext_get_allocated_storage(key_data: *const u8, key_len: u32, written_out: *mut u32) -> *mut u8;
@@ -142,7 +143,15 @@ pub trait Printable {
 impl<'a> Printable for &'a [u8] {
 	fn print(self) {
 		unsafe {
-			ext_print(self.as_ptr(), self.len() as u32);
+			ext_print_hex(self.as_ptr(), self.len() as u32);
+		}
+	}
+}
+
+impl<'a> Printable for &'a str {
+	fn print(self) {
+		unsafe {
+			ext_print_utf8(self.as_ptr() as *const u8, self.len() as u32);
 		}
 	}
 }
diff --git a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.compact.wasm b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.compact.wasm
index 9a03a7370d..9bf101d73f 100644
Binary files a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.compact.wasm and b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.compact.wasm differ
diff --git a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.wasm b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.wasm
index 7c56e0c5d7..6cbc2ef9b9 100644
Binary files a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.wasm and b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_polkadot.wasm differ
diff --git a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm
index 2e00c051fd..6005dbbca5 100644
Binary files a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm and b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm differ
diff --git a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.wasm b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.wasm
index e8be4d6d0c..45e9c3bf23 100644
Binary files a/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.wasm and b/substrate/wasm-runtime/target/wasm32-unknown-unknown/release/runtime_test.wasm differ
diff --git a/substrate/wasm-runtime/test/src/lib.rs b/substrate/wasm-runtime/test/src/lib.rs
index ed4610a4df..caa34856f4 100644
--- a/substrate/wasm-runtime/test/src/lib.rs
+++ b/substrate/wasm-runtime/test/src/lib.rs
@@ -30,16 +30,16 @@ fn test_ed25519_verify(input: &[u8]) -> Vec<u8> {
 }
 
 fn test_data_in(input: &[u8]) -> Vec<u8> {
-	print(b"set_storage" as &[u8]);
+	print("set_storage");
 	set_storage(b"input", &input);
 
-	print(b"storage" as &[u8]);
+	print("storage");
 	let foo = storage(b"foo");
 
-	print(b"set_storage" as &[u8]);
+	print("set_storage");
 	set_storage(b"baz", &foo);
 
-	print(b"finished!" as &[u8]);
+	print("finished!");
 	b"all ok!".to_vec()
 }