diff --git a/app/src/main/java/com/github/yeriomin/yalpstore/AccountTypeDialogBuilder.java b/app/src/main/java/com/github/yeriomin/yalpstore/AccountTypeDialogBuilder.java
index 5f5fc6bc7..6ca94d12d 100644
--- a/app/src/main/java/com/github/yeriomin/yalpstore/AccountTypeDialogBuilder.java
+++ b/app/src/main/java/com/github/yeriomin/yalpstore/AccountTypeDialogBuilder.java
@@ -60,7 +60,7 @@ public class AccountTypeDialogBuilder extends CredentialsDialogBuilder {
         task.execute();
     }
 
-    abstract private class AppProvidedCredentialsTask extends CredentialsDialogBuilder.CheckCredentialsTask {
+    abstract private static class AppProvidedCredentialsTask extends CredentialsDialogBuilder.CheckCredentialsTask {
 
         abstract protected void payload() throws IOException;
 
@@ -80,7 +80,7 @@ public class AccountTypeDialogBuilder extends CredentialsDialogBuilder {
         }
     }
 
-    private class RefreshTokenTask extends AppProvidedCredentialsTask {
+    private static class RefreshTokenTask extends AppProvidedCredentialsTask {
 
         @Override
         public void setCaller(PlayStoreTask caller) {
@@ -94,7 +94,7 @@ public class AccountTypeDialogBuilder extends CredentialsDialogBuilder {
         }
     }
 
-    private class LoginTask extends AppProvidedCredentialsTask {
+    private static class LoginTask extends AppProvidedCredentialsTask {
 
         @Override
         protected void payload() throws IOException {
diff --git a/app/src/main/java/com/github/yeriomin/yalpstore/CredentialsDialogBuilder.java b/app/src/main/java/com/github/yeriomin/yalpstore/CredentialsDialogBuilder.java
index 0f724b0fa..57e84fe52 100644
--- a/app/src/main/java/com/github/yeriomin/yalpstore/CredentialsDialogBuilder.java
+++ b/app/src/main/java/com/github/yeriomin/yalpstore/CredentialsDialogBuilder.java
@@ -33,7 +33,7 @@ abstract public class CredentialsDialogBuilder {
 
     abstract public Dialog show();
 
-    abstract protected class CheckCredentialsTask extends PlayStoreTask<Void> {
+    abstract protected static class CheckCredentialsTask extends PlayStoreTask<Void> {
 
         protected PlayStoreTask caller;
 
diff --git a/app/src/main/java/com/github/yeriomin/yalpstore/UserProvidedAccountDialogBuilder.java b/app/src/main/java/com/github/yeriomin/yalpstore/UserProvidedAccountDialogBuilder.java
index 0f8cf95f4..6d19a51cc 100644
--- a/app/src/main/java/com/github/yeriomin/yalpstore/UserProvidedAccountDialogBuilder.java
+++ b/app/src/main/java/com/github/yeriomin/yalpstore/UserProvidedAccountDialogBuilder.java
@@ -85,19 +85,13 @@ public class UserProvidedAccountDialogBuilder extends CredentialsDialogBuilder {
         return editEmail;
     }
 
-    private void addUsedEmail(String email) {
-        Set<String> emailsSet = Util.getStringSet(context, USED_EMAILS_SET);
-        emailsSet.add(email);
-        Util.putStringSet(context, USED_EMAILS_SET, emailsSet);
-    }
-
     private List<String> getUsedEmails() {
         List<String> emails = new ArrayList<>(Util.getStringSet(context, USED_EMAILS_SET));
         Collections.sort(emails);
         return emails;
     }
 
-    private class UserProvidedCredentialsTask extends CredentialsDialogBuilder.CheckCredentialsTask {
+    private static class UserProvidedCredentialsTask extends CredentialsDialogBuilder.CheckCredentialsTask {
 
         private String previousEmail;
 
@@ -129,5 +123,11 @@ public class UserProvidedAccountDialogBuilder extends CredentialsDialogBuilder {
             }
             return null;
         }
+
+        private void addUsedEmail(String email) {
+            Set<String> emailsSet = Util.getStringSet(context, USED_EMAILS_SET);
+            emailsSet.add(email);
+            Util.putStringSet(context, USED_EMAILS_SET, emailsSet);
+        }
     }
 }