diff --git a/calculatorpp/src/main/java/org/solovyev/android/AndroidUtils2.java b/calculatorpp/src/main/java/org/solovyev/android/AndroidUtils2.java
index 9abe58ae..1b073d4d 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/AndroidUtils2.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/AndroidUtils2.java
@@ -1,5 +1,6 @@
 package org.solovyev.android;
 
+import android.content.res.Configuration;
 import android.support.v4.app.DialogFragment;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
@@ -32,4 +33,11 @@ public final class AndroidUtils2 {
         dialogFragment.show(ft, fragmentTag);
 
     }
+
+    // copied from API-15
+    public static boolean isLayoutSizeAtLeast(int size, @NotNull Configuration configuration) {
+        int cur = configuration.screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK;
+        if (cur == Configuration.SCREENLAYOUT_SIZE_UNDEFINED) return false;
+        return cur >= size;
+    }
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
index 77b1b474..94478fd2 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
@@ -15,6 +15,7 @@ import jscl.NumeralBase;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.AndroidUtils;
+import org.solovyev.android.AndroidUtils2;
 import org.solovyev.android.calculator.model.AndroidCalculatorEngine;
 import org.solovyev.android.calculator.view.AngleUnitsButton;
 import org.solovyev.android.calculator.view.NumeralBasesButton;
@@ -59,11 +60,13 @@ public final class CalculatorButtons {
         }
     }
 
+
+
     public static void toggleEqualsButton(@Nullable SharedPreferences preferences,
                                           @NotNull Activity activity) {
         preferences = preferences == null ? PreferenceManager.getDefaultSharedPreferences(activity) : preferences;
 
-        final boolean large = activity.getResources().getConfiguration().isLayoutSizeAtLeast(Configuration.SCREENLAYOUT_SIZE_LARGE);
+        final boolean large = AndroidUtils2.isLayoutSizeAtLeast(Configuration.SCREENLAYOUT_SIZE_LARGE, activity.getResources().getConfiguration());
 
         if (!large) {
             if (AndroidUtils.getScreenOrientation(activity) == Configuration.ORIENTATION_PORTRAIT