diff --git a/Makefile b/Makefile
index 9e05038..70039db 100755
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 TESTS = test/mysql/*.js test/mssql/*.js test/*.js
-#TESTS = test/mssql/05-tests-multiple-pools.js
+#TESTS = test/mysql/03-tests-update_batch.js
 #TESTS = test/05-multiple-drivers.js
 test:
 	mocha --timeout 5000 --reporter spec $(TESTS)
diff --git a/drivers/query_builder.js b/drivers/query_builder.js
index 0323ce6..346ccd4 100755
--- a/drivers/query_builder.js
+++ b/drivers/query_builder.js
@@ -1529,8 +1529,18 @@ class GenericQueryBuilder {
                cases += `ELSE ${l} END, `;
            }
 
+           // Remove the trailing comma
            sql += cases.substr(0, cases.length - 2);
-           sql += ` WHERE ${where + index} IN (${ids.join(',')})`;
+
+           // Make sure we don't double-up on the "WHERE" directive
+           if (where) {
+               sql += ` ${where}`;
+           } else {
+               sql += ' WHERE ';
+           }
+
+
+           sql += `${index} IN (${ids.join(',')})`;
 
            // Add query to batch
            batches.push(sql);
diff --git a/test/mysql/03-tests-update_batch.js b/test/mysql/03-tests-update_batch.js
index be4ddea..673a6ea 100755
--- a/test/mysql/03-tests-update_batch.js
+++ b/test/mysql/03-tests-update_batch.js
@@ -3,7 +3,7 @@ const expect = require('chai').expect;
 const QueryBuilder = require('../../drivers/mysql/query_builder.js');
 const qb = new QueryBuilder();
 
-const test_where = {id:3};
+const test_where = {quadrant: 'Alpha'};
 const test_data = [{id:3, name:'Milky Way', type: 'spiral'}, {id:4, name: 'Andromeda', type: 'spiral'}];
 
 describe('MySQL: update_batch()', () => {
@@ -18,4 +18,9 @@ describe('MySQL: update_batch()', () => {
         const sql = qb.update_batch('galaxies', test_data, 'id');
         sql.should.eql(["UPDATE (`galaxies`) SET `name` = CASE WHEN `id` = 3 THEN 'Milky Way' WHEN `id` = 4 THEN 'Andromeda' ELSE `name` END, `type` = CASE WHEN `id` = 3 THEN 'spiral' WHEN `id` = 4 THEN 'spiral' ELSE `type` END WHERE `id` IN (3,4)"]);
     });
+    it('should build a proper batch UPDATE string when where clause is provided', () => {
+        qb.reset_query();
+        const sql = qb.update_batch('galaxies', test_data, 'id', test_where);
+        sql.should.eql(["UPDATE (`galaxies`) SET `name` = CASE WHEN `id` = 3 THEN 'Milky Way' WHEN `id` = 4 THEN 'Andromeda' ELSE `name` END, `type` = CASE WHEN `id` = 3 THEN 'spiral' WHEN `id` = 4 THEN 'spiral' ELSE `type` END WHERE `quadrant` = 'Alpha' AND `id` IN (3,4)"]);
+    });
 });