diff --git a/engines/node/store-engine/sql.js b/engines/node/store-engine/sql.js
index d0f2ee9..d5bfbe3 100644
--- a/engines/node/store-engine/sql.js
+++ b/engines/node/store-engine/sql.js
@@ -4,7 +4,8 @@
  * Currently only supports MySQL.
  */
 
-var DatabaseError = require('perstore/errors').DatabaseError;
+var DatabaseError = require('perstore/errors').DatabaseError,
+	DuplicateEntryError = require('perstore/errors').DuplicateEntryError;
 
 var engines = {
 	mysql: MysqlWrapper
@@ -36,19 +37,26 @@ function MysqlWrapper(params) {
 			if(charset && charset.name=="utf8") conn.execute("SET NAMES utf8");
 			var cmd = conn.execute(query,args);
 
-			cmd.on('result', function() {
+			// use result from callback
+			cmd.on('result', function(result) {
 				if (conn.clean && callback) {
 					callback({
-						insertId: cmd.result.insert_id,
-						rowsAffected: cmd.result.affected_rows,
-						rows: cmd.result.rows
+						insertId: result.insert_id,
+						rowsAffected: result.affected_rows,
+						rows: result.rows
 					});
 				}
 			});
 			cmd.on('error', function(err) {
 				conn.clean = false;
-				if (errback)
-					errback(err);
+				if(errback) {
+					var patt=/^duplicate entry/ig;
+					if(err && patt.test(err.message)) {
+						errback(new DuplicateEntryError(err.message));
+					} else {
+						errback(err);
+					}
+				}
 			});
 		},
 		transaction: function() {
@@ -91,6 +99,8 @@ function MysqlWrapper(params) {
 		ret.row_as_hash = true;
 		ret.clean = true;
 
+		// use charset if available
+		if(params.charset) ret.set("charset",params.charset);
 		throwOnError(ret.connection, 'connect to DB');
 		throwOnError(ret.auth(params.name, params.username, params.password), 'authenticate');
 
diff --git a/errors.js b/errors.js
index c08423e..7bd97ac 100644
--- a/errors.js
+++ b/errors.js
@@ -10,3 +10,8 @@ NotFoundError.prototype.code = 2;
 
 var PreconditionFailed = exports.PreconditionFailed = ErrorConstructor("PreconditionFailed", DatabaseError);
 PreconditionFailed.prototype.code = 3;
+
+var DuplicateEntryError = exports.DuplicateEntryError = ErrorConstructor("DuplicateEntryError", DatabaseError);
+DuplicateEntryError.prototype.code = 4;
+
+var AcceptError = exports.AcceptError = ErrorConstructor("AcceptError");
\ No newline at end of file
diff --git a/store/mongodb.js b/store/mongodb.js
index 23c1e30..48faf2c 100644
--- a/store/mongodb.js
+++ b/store/mongodb.js
@@ -20,7 +20,8 @@ var convertNodeAsyncFunction = require('promised-io/promise').convertNodeAsyncFu
 	defer = require("promised-io/promise").defer,
 	when = require("promised-io/promise").when,
 	jsArray = require("rql/js-array"),
-	PreconditionFailed = require("../errors").PreconditionFailed;
+	PreconditionFailed = require("../errors").PreconditionFailed,
+	DuplicateEntryError = require('perstore/errors').DuplicateEntryError;
 
 var RQ = require("rql/parser");
 //RQ.converters["default"] = exports.converters.auto;
@@ -279,7 +280,7 @@ module.exports = function(options){
 							deferred.resolve(obj.id);
 						});
 					} else {
-						deferred.reject(id + " exists, and can't be overwritten");
+						deferred.reject(new DuplicateEntryError(id + " exists, and can't be overwritten"));
 					}
 				});
 			} else {