diff --git a/calculatorpp/AndroidManifest.xml b/calculatorpp/AndroidManifest.xml
index d7ff4562..f069c6c3 100644
--- a/calculatorpp/AndroidManifest.xml
+++ b/calculatorpp/AndroidManifest.xml
@@ -7,7 +7,7 @@
     <uses-permission android:name="com.android.vending.BILLING"/>
 
     <!--TODO: REMOVE IN PRODUCTION-->
-    <uses-permission android:name="android.permission.DISABLE_KEYGUARD"/>
+    <!--<uses-permission android:name="android.permission.DISABLE_KEYGUARD"/>-->
 
     <!-- for onscreen -->
     <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
index 7129c58b..def27e3a 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
@@ -4,6 +4,7 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
 import android.preference.PreferenceManager;
+import android.util.Log;
 import net.robotmedia.billing.BillingController;
 import net.robotmedia.billing.helper.DefaultBillingObserver;
 import net.robotmedia.billing.model.BillingDB;
@@ -118,6 +119,15 @@ public class CalculatorApplication extends android.app.Application {
             public void run() {
                 BillingController.checkBillingSupported(CalculatorApplication.this);
                 AdsController.getInstance().isAdFree(CalculatorApplication.this);
+
+                try {
+                    // prepare engine
+                    Locator.getInstance().getEngine().getMathEngine0().evaluate("1+1");
+                    Locator.getInstance().getEngine().getMathEngine0().evaluate("1*1");
+                } catch (Throwable e) {
+                    Log.e(TAG, e.getMessage(), e);
+                }
+
             }
         }).start();