diff --git a/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpMockServer.groovy b/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpMockServer.groovy
index 3ec1ece..7d2f86b 100644
--- a/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpMockServer.groovy
+++ b/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpMockServer.groovy
@@ -22,6 +22,8 @@ import pl.touk.mockserver.api.response.Parameter
 import javax.xml.bind.JAXBContext
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.CopyOnWriteArraySet
+import java.util.concurrent.Executor
+import java.util.concurrent.Executors
 
 import static pl.touk.mockserver.server.Util.createResponse
 
@@ -32,12 +34,14 @@ class HttpMockServer {
     private final Map<Integer, HttpServerWraper> childServers = new ConcurrentHashMap<>()
     private final Set<String> mockNames = new CopyOnWriteArraySet<>()
     private final ConfigObject configuration = new ConfigObject()
+    private final Executor executor
 
     private static
     final JAXBContext requestJaxbContext = JAXBContext.newInstance(AddMock.package.name, AddMock.classLoader)
 
-    HttpMockServer(int port = 9999, ConfigObject initialConfiguration = new ConfigObject()) {
-        httpServerWraper = new HttpServerWraper(port)
+    HttpMockServer(int port = 9999, ConfigObject initialConfiguration = new ConfigObject(), int threads = 10) {
+        executor = Executors.newFixedThreadPool(threads)
+        httpServerWraper = new HttpServerWraper(port, executor)
 
         initialConfiguration.values()?.each { ConfigObject co ->
             addMock(co)
@@ -172,7 +176,7 @@ class HttpMockServer {
     private HttpServerWraper getOrCreateChildServer(int mockPort) {
         HttpServerWraper child = childServers[mockPort]
         if (!child) {
-            child = new HttpServerWraper(mockPort)
+            child = new HttpServerWraper(mockPort, executor)
             childServers.put(mockPort, child)
         }
         return child
diff --git a/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpServerWraper.groovy b/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpServerWraper.groovy
index b13b7a2..e1ef2f8 100644
--- a/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpServerWraper.groovy
+++ b/mockserver/src/main/groovy/pl/touk/mockserver/server/HttpServerWraper.groovy
@@ -5,7 +5,7 @@ import com.sun.net.httpserver.HttpServer
 import groovy.transform.PackageScope
 import groovy.util.logging.Slf4j
 
-import java.util.concurrent.Executors
+import java.util.concurrent.Executor
 
 @Slf4j
 @PackageScope
@@ -15,11 +15,11 @@ class HttpServerWraper {
 
     private List<ContextExecutor> executors = []
 
-    HttpServerWraper(int port) {
+    HttpServerWraper(int port, Executor executor) {
         this.port = port
         InetSocketAddress addr = new InetSocketAddress(Inet4Address.getByName("0.0.0.0"), port)
         httpServer = HttpServer.create(addr, 0)
-        httpServer.executor = Executors.newWorkStealingPool()
+        httpServer.executor = executor
         log.info("Http server starting on port $port...")
         httpServer.start()
         log.info('Http server is started')
diff --git a/mockserver/src/main/groovy/pl/touk/mockserver/server/Main.groovy b/mockserver/src/main/groovy/pl/touk/mockserver/server/Main.groovy
index aba7f6e..0b8d42a 100644
--- a/mockserver/src/main/groovy/pl/touk/mockserver/server/Main.groovy
+++ b/mockserver/src/main/groovy/pl/touk/mockserver/server/Main.groovy
@@ -21,9 +21,11 @@ class Main {
     private static HttpMockServer startMockServer(String... args) {
         switch (args.length) {
             case 1:
-                return new HttpMockServer(args[0] as int)
+                return new HttpMockServer(args[0] as int, new ConfigObject())
             case 2:
                 return new HttpMockServer(args[0] as int, new ConfigSlurper().parse(new File(args[1]).toURI().toURL()))
+            case 3:
+                return new HttpMockServer(args[0] as int, new ConfigSlurper().parse(new File(args[1]).toURI().toURL()), args[2] as int)
             default:
                 return new HttpMockServer()
         }
diff --git a/mockserver/src/main/groovy/pl/touk/mockserver/server/Mock.groovy b/mockserver/src/main/groovy/pl/touk/mockserver/server/Mock.groovy
index db67f47..83c3c7e 100644
--- a/mockserver/src/main/groovy/pl/touk/mockserver/server/Mock.groovy
+++ b/mockserver/src/main/groovy/pl/touk/mockserver/server/Mock.groovy
@@ -103,7 +103,9 @@ class Mock implements Comparable<Mock> {
         }
         compilerConfiguration.addCompilationCustomizers(customizer)
         GroovyShell sh = new GroovyShell(this.class.classLoader, compilerConfiguration);
-        return sh.evaluate(predicate) as Closure
+        Closure closure = sh.evaluate(predicate) as Closure
+        sh.resetLoadedClasses()
+        return closure
     }
 
     void setResponse(String response) {
diff --git a/pom.xml b/pom.xml
index 35dac1a..635fed9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,7 +24,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <maven-compiler-plugin.version>3.1</maven-compiler-plugin.version>
-        <groovy.version>2.4.1</groovy.version>
+        <groovy.version>2.4.11</groovy.version>
         <httpclient.version>4.3.5</httpclient.version>
         <spock-core.version>1.0-groovy-2.4</spock-core.version>
         <commons-lang3.version>3.3.2</commons-lang3.version>