diff --git a/util/src/journaldb/archivedb.rs b/util/src/journaldb/archivedb.rs
index c6acc1280..e971711e0 100644
--- a/util/src/journaldb/archivedb.rs
+++ b/util/src/journaldb/archivedb.rs
@@ -20,6 +20,7 @@ use common::*;
 use rlp::*;
 use hashdb::*;
 use memorydb::*;
+use super::{DB_PREFIX_LEN, LATEST_ERA_KEY, VERSION_KEY};
 use super::traits::JournalDB;
 use kvdb::{Database, DBTransaction, DatabaseConfig};
 #[cfg(test)]
@@ -38,17 +39,14 @@ pub struct ArchiveDB {
 	latest_era: Option<u64>,
 }
 
-// all keys must be at least 12 bytes
-const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
-const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
 const DB_VERSION : u32 = 0x103;
 
 impl ArchiveDB {
 	/// Create a new instance from file
 	pub fn new(path: &str) -> ArchiveDB {
 		let opts = DatabaseConfig {
-			//use 12 bytes as prefix, this must match account_db prefix
-			prefix_size: Some(12),
+			// this must match account_db prefix
+			prefix_size: Some(DB_PREFIX_LEN),
 			max_open_files: 256,
 		};
 		let backing = Database::open(&opts, path).unwrap_or_else(|e| {
diff --git a/util/src/journaldb/earlymergedb.rs b/util/src/journaldb/earlymergedb.rs
index 7cb117447..4d897e3db 100644
--- a/util/src/journaldb/earlymergedb.rs
+++ b/util/src/journaldb/earlymergedb.rs
@@ -20,6 +20,7 @@ use common::*;
 use rlp::*;
 use hashdb::*;
 use memorydb::*;
+use super::{DB_PREFIX_LEN, LATEST_ERA_KEY, VERSION_KEY};
 use super::traits::JournalDB;
 use kvdb::{Database, DBTransaction, DatabaseConfig};
 #[cfg(test)]
@@ -67,9 +68,6 @@ pub struct EarlyMergeDB {
 	latest_era: Option<u64>,
 }
 
-// all keys must be at least 12 bytes
-const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
-const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
 const DB_VERSION : u32 = 0x003;
 const PADDING : [u8; 10] = [ 0u8; 10 ];
 
@@ -77,8 +75,8 @@ impl EarlyMergeDB {
 	/// Create a new instance from file
 	pub fn new(path: &str) -> EarlyMergeDB {
 		let opts = DatabaseConfig {
-			//use 12 bytes as prefix, this must match account_db prefix
-			prefix_size: Some(12),
+			// this must match account_db prefix
+			prefix_size: Some(DB_PREFIX_LEN),
 			max_open_files: 256,
 		};
 		let backing = Database::open(&opts, path).unwrap_or_else(|e| {
diff --git a/util/src/journaldb/mod.rs b/util/src/journaldb/mod.rs
index 6e389b3c0..9f242e950 100644
--- a/util/src/journaldb/mod.rs
+++ b/util/src/journaldb/mod.rs
@@ -79,3 +79,8 @@ pub fn new(path: &str, algorithm: Algorithm) -> Box<JournalDB> {
 		Algorithm::RefCounted => Box::new(refcounteddb::RefCountedDB::new(path)),
 	}
 }
+
+// all keys must be at least 12 bytes
+const DB_PREFIX_LEN : usize = 12;
+const LATEST_ERA_KEY : [u8; DB_PREFIX_LEN] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
+const VERSION_KEY : [u8; DB_PREFIX_LEN] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
diff --git a/util/src/journaldb/overlayrecentdb.rs b/util/src/journaldb/overlayrecentdb.rs
index 86d8d5c4d..435dd7880 100644
--- a/util/src/journaldb/overlayrecentdb.rs
+++ b/util/src/journaldb/overlayrecentdb.rs
@@ -20,6 +20,7 @@ use common::*;
 use rlp::*;
 use hashdb::*;
 use memorydb::*;
+use super::{DB_PREFIX_LEN, LATEST_ERA_KEY, VERSION_KEY};
 use kvdb::{Database, DBTransaction, DatabaseConfig};
 #[cfg(test)]
 use std::env;
@@ -92,9 +93,6 @@ impl Clone for OverlayRecentDB {
 	}
 }
 
-// all keys must be at least 12 bytes
-const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
-const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
 const DB_VERSION : u32 = 0x203;
 const PADDING : [u8; 10] = [ 0u8; 10 ];
 
@@ -107,8 +105,8 @@ impl OverlayRecentDB {
 	/// Create a new instance from file
 	pub fn from_prefs(path: &str) -> OverlayRecentDB {
 		let opts = DatabaseConfig {
-			//use 12 bytes as prefix, this must match account_db prefix
-			prefix_size: Some(12),
+			// this must match account_db prefix
+			prefix_size: Some(DB_PREFIX_LEN),
 			max_open_files: 256,
 		};
 		let backing = Database::open(&opts, path).unwrap_or_else(|e| {
diff --git a/util/src/journaldb/refcounteddb.rs b/util/src/journaldb/refcounteddb.rs
index 7f24a729c..3bcb0faaf 100644
--- a/util/src/journaldb/refcounteddb.rs
+++ b/util/src/journaldb/refcounteddb.rs
@@ -20,6 +20,7 @@ use common::*;
 use rlp::*;
 use hashdb::*;
 use overlaydb::*;
+use super::{DB_PREFIX_LEN, LATEST_ERA_KEY, VERSION_KEY};
 use super::traits::JournalDB;
 use kvdb::{Database, DBTransaction, DatabaseConfig};
 #[cfg(test)]
@@ -40,8 +41,6 @@ pub struct RefCountedDB {
 	removes: Vec<H256>,
 }
 
-const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
-const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
 const DB_VERSION : u32 = 0x200;
 const PADDING : [u8; 10] = [ 0u8; 10 ];
 
@@ -49,8 +48,8 @@ impl RefCountedDB {
 	/// Create a new instance given a `backing` database.
 	pub fn new(path: &str) -> RefCountedDB {
 		let opts = DatabaseConfig {
-			//use 12 bytes as prefix, this must match account_db prefix
-			prefix_size: Some(12),
+			// this must match account_db prefix
+			prefix_size: Some(DB_PREFIX_LEN),
 			max_open_files: 256,
 		};
 		let backing = Database::open(&opts, path).unwrap_or_else(|e| {