diff --git a/src/main/java/ru/touchin/roboswag/core/observables/storable/Migration.java b/src/main/java/ru/touchin/roboswag/core/observables/storable/Migration.java
index 42f6059..0f36f5e 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/storable/Migration.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/storable/Migration.java
@@ -63,6 +63,21 @@ public class Migration<TKey> {
                         -> Single.error(new MigrationException(String.format("Can't get version of '%s' from %s", key, versionsStore), throwable)));
     }
 
+    @NonNull
+    private Single<Long> makeMigrationChain(@NonNull final TKey key, @NonNull final VersionUpdater versionUpdater) {
+        Single<Long> chain = Single.fromCallable(() -> versionUpdater.initialVersion);
+        for (final Migrator<TKey, ?, ?> migrator : migrators) {
+            chain = chain.flatMap(updatedVersion ->
+                    migrator.canMigrate(key, updatedVersion)
+                            .flatMap(canMigrate -> canMigrate
+                                    ? migrator.migrate(key, updatedVersion)
+                                    .doOnSuccess(newVersion
+                                            -> versionUpdater.updateVersion(newVersion, latestVersion, migrator))
+                                    : Single.just(updatedVersion)));
+        }
+        return chain;
+    }
+
     /**
      * Migrates some object by key to latest version.
      *
@@ -73,17 +88,7 @@ public class Migration<TKey> {
         return loadCurrentVersion(key)
                 .flatMap(currentVersion -> {
                     final VersionUpdater versionUpdater = new VersionUpdater<>(key, versionsStore, currentVersion);
-                    Single<Long> chain = Single.fromCallable(() -> versionUpdater.initialVersion);
-                    for (final Migrator<TKey, ?, ?> migrator : migrators) {
-                        chain = chain.flatMap(updatedVersion ->
-                                migrator.canMigrate(key, updatedVersion)
-                                        .flatMap(canMigrate -> canMigrate
-                                                ? migrator.migrate(key, updatedVersion)
-                                                .doOnSuccess(newVersion
-                                                        -> versionUpdater.updateVersion(newVersion, latestVersion, migrator))
-                                                : Single.just(updatedVersion)));
-                    }
-                    return chain
+                    return makeMigrationChain(key, versionUpdater)
                             .doOnSuccess(lastUpdatedVersion -> {
                                 if (lastUpdatedVersion < latestVersion) {
                                     throw OnErrorThrowable.from(new NextLoopMigrationException());
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/storable/Storable.java b/src/main/java/ru/touchin/roboswag/core/observables/storable/Storable.java
index dc532ab..1c362e8 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/storable/Storable.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/storable/Storable.java
@@ -105,7 +105,8 @@ public class Storable<TKey, TObject, TStoreObject> {
         this.storeObjectType = storeObjectType;
         this.store = store;
         this.converter = converter;
-        final ObserveStrategy nonNullObserveStrategy = observeStrategy != null ? observeStrategy : getDefaultObserveStrategyFor(objectType, storeObjectType);
+        final ObserveStrategy nonNullObserveStrategy
+                = observeStrategy != null ? observeStrategy : getDefaultObserveStrategyFor(objectType, storeObjectType);
         scheduler = storeScheduler != null ? storeScheduler : Schedulers.from(Executors.newSingleThreadExecutor());
         storeValueObservable
                 = createStoreValueObservable(nonNullObserveStrategy, migration, defaultValue);
@@ -390,6 +391,8 @@ public class Storable<TKey, TObject, TStoreObject> {
                     sourceBuilder.migration, sourceBuilder.defaultValue, sourceBuilder.storeScheduler);
         }
 
+        @SuppressWarnings("CPD-START")
+        //CPD: it is same code as constructor of Storable
         private BuilderCore(@NonNull final TKey key,
                             @NonNull final Type objectType,
                             @NonNull final Type storeObjectType,
@@ -410,6 +413,7 @@ public class Storable<TKey, TObject, TStoreObject> {
             this.storeScheduler = storeScheduler;
         }
 
+        @SuppressWarnings("CPD-END")
         protected void setStoreSchedulerInternal(@Nullable final Scheduler storeScheduler) {
             this.storeScheduler = storeScheduler;
         }
@@ -507,11 +511,6 @@ public class Storable<TKey, TObject, TStoreObject> {
             return new Storable<>(this);
         }
 
-        @Override
-        protected void setObserveStrategyInternal(@Nullable final ObserveStrategy observeStrategy) {
-            super.setObserveStrategyInternal(observeStrategy);
-        }
-
     }
 
 }
diff --git a/src/main/java/ru/touchin/roboswag/core/observables/storable/concrete/NonNullStorable.java b/src/main/java/ru/touchin/roboswag/core/observables/storable/concrete/NonNullStorable.java
index 16840a9..95dc8ec 100644
--- a/src/main/java/ru/touchin/roboswag/core/observables/storable/concrete/NonNullStorable.java
+++ b/src/main/java/ru/touchin/roboswag/core/observables/storable/concrete/NonNullStorable.java
@@ -42,7 +42,7 @@ public class NonNullStorable<TKey, TObject, TStoreObject> extends Storable<TKey,
 
     @NonNull
     @Override
-    public TObject getSync() {
+    public TObject getSync() throws Throwable {
         final TObject result = super.getSync();
         if (result == null) {
             throw new ShouldNotHappenException();