diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java b/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
index fa4115fc..55a700e8 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorApplication.java
@@ -87,7 +87,7 @@ public class CalculatorApplication extends android.app.Application {
 
 			@Override
 			public String getPublicKey() {
-				return CalculatorSecurity.PK;
+				return CalculatorSecurity.getPK();
 			}
 		});
 		BillingController.checkBillingSupported(this);
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorSecurity.java b/src/main/java/org/solovyev/android/calculator/CalculatorSecurity.java
index d97d8423..b6786289 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorSecurity.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorSecurity.java
@@ -6,6 +6,8 @@
 
 package org.solovyev.android.calculator;
 
+import org.jetbrains.annotations.NotNull;
+
 /**
  * User: serso
  * Date: 1/4/12
@@ -13,8 +15,11 @@ package org.solovyev.android.calculator;
  */
 public final class CalculatorSecurity {
 
-	public static final String PK = "org.solovyev.android.calculator";
-
 	private CalculatorSecurity() {
 	}
+
+	@NotNull
+	public static String getPK() {
+		return "org.solovyev.android.calculator";
+	}
 }