diff --git a/.idea/artifacts/KotlinPlugin.xml b/.idea/artifacts/KotlinPlugin.xml
index c21183dae2c..d070d3e2400 100644
--- a/.idea/artifacts/KotlinPlugin.xml
+++ b/.idea/artifacts/KotlinPlugin.xml
@@ -32,6 +32,7 @@
               <element id="module-output" name="ide-compiler-runner" />
               <element id="module-output" name="cli-common" />
               <element id="module-output" name="util" />
+              <element id="module-output" name="preloader" />
             </element>
           </element>
         </element>
diff --git a/ide-compiler-runner/ide-compiler-runner.iml b/ide-compiler-runner/ide-compiler-runner.iml
index 4707ed53d80..6b04cf366d7 100644
--- a/ide-compiler-runner/ide-compiler-runner.iml
+++ b/ide-compiler-runner/ide-compiler-runner.iml
@@ -10,6 +10,7 @@
     <orderEntry type="library" name="idea-full" level="project" />
     <orderEntry type="module" module-name="cli-common" />
     <orderEntry type="module" module-name="util" />
+    <orderEntry type="module" module-name="preloader" />
   </component>
 </module>
 
diff --git a/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/CompilerRunnerUtil.java b/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/CompilerRunnerUtil.java
index bff91dc1e6d..e37c7bca203 100644
--- a/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/CompilerRunnerUtil.java
+++ b/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/CompilerRunnerUtil.java
@@ -19,6 +19,7 @@ package org.jetbrains.jet.compiler.runner;
 import com.intellij.util.Function;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.cli.common.messages.*;
+import org.jetbrains.jet.preloading.ClassPreloadingUtils;
 import org.jetbrains.jet.utils.KotlinPaths;
 
 import java.io.*;
@@ -35,7 +36,7 @@ import static org.jetbrains.jet.cli.common.messages.CompilerMessageSeverity.*;
 
 public class CompilerRunnerUtil {
 
-    private static SoftReference<URLClassLoader> ourClassLoaderRef = new SoftReference<URLClassLoader>(null);
+    private static SoftReference<ClassLoader> ourClassLoaderRef = new SoftReference<ClassLoader>(null);
 
     public static List<File> kompilerClasspath(KotlinPaths paths, MessageCollector messageCollector) {
         File libs = paths.getLibPath();
@@ -50,11 +51,26 @@ public class CompilerRunnerUtil {
         return answer;
     }
 
-    public static URLClassLoader getOrCreateClassLoader(KotlinPaths paths, MessageCollector messageCollector) {
-        URLClassLoader answer = ourClassLoaderRef.get();
+    public static ClassLoader getOrCreatePreloader(KotlinPaths paths, MessageCollector messageCollector) {
+        ClassLoader answer = ourClassLoaderRef.get();
+        if (answer == null) {
+            try {
+                int estimatedClassNumber = 4096;
+                answer = ClassPreloadingUtils.preloadClasses(kompilerClasspath(paths, messageCollector), estimatedClassNumber, null);
+            }
+            catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+            ourClassLoaderRef = new SoftReference<ClassLoader>(answer);
+        }
+        return answer;
+    }
+
+    public static ClassLoader getOrCreateClassLoader(KotlinPaths paths, MessageCollector messageCollector) {
+        ClassLoader answer = ourClassLoaderRef.get();
         if (answer == null) {
             answer = createClassloader(paths, messageCollector);
-            ourClassLoaderRef = new SoftReference<URLClassLoader>(answer);
+            ourClassLoaderRef = new SoftReference<ClassLoader>(answer);
         }
         return answer;
     }
@@ -90,9 +106,11 @@ public class CompilerRunnerUtil {
 
     public static Object invokeExecMethod(
             String className, String[] arguments, CompilerEnvironment environment,
-            MessageCollector messageCollector, PrintStream out
+            MessageCollector messageCollector, PrintStream out, boolean usePreloader
     ) throws Exception {
-        URLClassLoader loader = getOrCreateClassLoader(environment.getKotlinPaths(), messageCollector);
+        ClassLoader loader = usePreloader
+                             ? getOrCreatePreloader(environment.getKotlinPaths(), messageCollector)
+                             : getOrCreateClassLoader(environment.getKotlinPaths(), messageCollector);
         Class<?> kompiler = Class.forName(className, true, loader);
         Method exec = kompiler.getMethod("exec", PrintStream.class, String[].class);
         return exec.invoke(kompiler.newInstance(), out, arguments);
diff --git a/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/KotlinCompilerRunner.java b/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/KotlinCompilerRunner.java
index e9afc3f6de3..7737a7fac94 100644
--- a/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/KotlinCompilerRunner.java
+++ b/ide-compiler-runner/src/org/jetbrains/jet/compiler/runner/KotlinCompilerRunner.java
@@ -74,7 +74,8 @@ public class KotlinCompilerRunner {
             messageCollector.report(CompilerMessageSeverity.INFO,
                                "Invoking in-process compiler " + compilerClassName + " with arguments " + Arrays.asList(arguments),
                                CompilerMessageLocation.NO_LOCATION);
-            Object rc = CompilerRunnerUtil.invokeExecMethod(compilerClassName, arguments, environment, messageCollector, out);
+            Object rc = CompilerRunnerUtil.invokeExecMethod(compilerClassName, arguments, environment,
+                                                            messageCollector, out, /*usePreloader=*/true);
             // exec() returns a K2JVMCompiler.ExitCode object, that class is not accessible here,
             // so we take it's contents through reflection
             return CompilerRunnerUtil.getReturnCodeFromObject(rc);
diff --git a/idea/src/org/jetbrains/jet/plugin/compiler/K2JSCompiler.java b/idea/src/org/jetbrains/jet/plugin/compiler/K2JSCompiler.java
index 5be4ece9d5a..6cdecbeeff2 100644
--- a/idea/src/org/jetbrains/jet/plugin/compiler/K2JSCompiler.java
+++ b/idea/src/org/jetbrains/jet/plugin/compiler/K2JSCompiler.java
@@ -129,7 +129,8 @@ public final class K2JSCompiler implements TranslatingCompiler {
         File outDir = environment.getOutput();
         File outFile = new File(outDir, module.getName() + ".js");
         String[] commandLineArgs = constructArguments(module, outFile);
-        Object rc = invokeExecMethod("org.jetbrains.jet.cli.js.K2JSCompiler", commandLineArgs, environment, messageCollector, out);
+        // No preloading for in-process compiler
+        Object rc = invokeExecMethod("org.jetbrains.jet.cli.js.K2JSCompiler", commandLineArgs, environment, messageCollector, out, false);
 
         if (!ApplicationManager.getApplication().isUnitTestMode()) {
             VirtualFile virtualFile = LocalFileSystem.getInstance().findFileByIoFile(outDir);