diff --git a/src/main/java/de/ids_mannheim/korap/oauth2/dao/OAuth2ClientDao.java b/src/main/java/de/ids_mannheim/korap/oauth2/dao/OAuth2ClientDao.java
index e7d23eb..2f3f35e 100644
--- a/src/main/java/de/ids_mannheim/korap/oauth2/dao/OAuth2ClientDao.java
+++ b/src/main/java/de/ids_mannheim/korap/oauth2/dao/OAuth2ClientDao.java
@@ -52,8 +52,8 @@
 	public void registerClient (boolean isSuper, String id,
 			String secretHashcode, String name, OAuth2ClientType type,
 			String url, String redirectURI, String registeredBy,
-			String description, int refreshTokenExpiry, JsonNode source,
-			boolean isPermitted) throws KustvaktException {
+			String description, int refreshTokenExpiry, JsonNode source) 
+			throws KustvaktException {
 		
 		ParameterChecker.checkStringValue(id, "client_id");
         ParameterChecker.checkStringValue(name, "client_name");
@@ -83,9 +83,7 @@
                 client.setSource(source.toString());
                 // setting permit for plugin, used in OAuth2TestBase
                 // this should be an admin function
-                if (isPermitted) { 
-                	client.setPermitted(isPermitted);
-                }
+            	client.setPermitted(false);
             }
             else {
                 throw new KustvaktException(StatusCodes.NOT_SUPPORTED,
@@ -115,14 +113,6 @@
         entityManager.persist(client);
 	}
     
-	public void registerClient (String id, String secretHashcode, String name,
-			OAuth2ClientType type, String url, String redirectURI,
-			String registeredBy, String description, int refreshTokenExpiry,
-			JsonNode source) throws KustvaktException {
-		registerClient(false, id, secretHashcode, name, type, url, redirectURI,
-				registeredBy, description, refreshTokenExpiry, source, false);
-	}
-
     public OAuth2Client retrieveClientById (String clientId)
             throws KustvaktException {
 
@@ -149,6 +139,32 @@
                     e.getMessage(), "invalid_client");
         }
     }
+    
+    // EM: used for testing only
+    public int retrieveSuperClients ()
+            throws KustvaktException {
+
+        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
+        CriteriaQuery<OAuth2Client> query = builder
+                .createQuery(OAuth2Client.class);
+
+        Root<OAuth2Client> root = query.from(OAuth2Client.class);
+        query.select(root);
+        query.where(builder.equal(root.get(OAuth2Client_.isSuper), true));
+
+        Query q = entityManager.createQuery(query);
+        try {
+            return q.getResultList().size();
+        }
+        catch (NoResultException e) {
+            throw new KustvaktException(StatusCodes.CLIENT_NOT_FOUND,
+                    "No super client found.");
+        }
+        catch (Exception e) {
+            throw new KustvaktException(StatusCodes.CLIENT_NOT_FOUND,
+                    e.getMessage(), "invalid_client");
+        }
+    }
 
     public void deregisterClient (OAuth2Client client)
             throws KustvaktException {
diff --git a/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java b/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
index 6d01bf2..3d4e3be 100644
--- a/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
+++ b/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
@@ -1,9 +1,5 @@
 package de.ids_mannheim.korap.oauth2.service;
 
-import java.net.MalformedURLException;
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.net.URL;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -16,7 +12,6 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.nimbusds.oauth2.sdk.OAuth2Error;
 
-import de.ids_mannheim.korap.config.FullConfiguration;
 import de.ids_mannheim.korap.dao.AdminDao;
 import de.ids_mannheim.korap.dto.InstalledPluginDto;
 import de.ids_mannheim.korap.encryption.RandomCodeGenerator;
@@ -88,12 +83,10 @@
     private EncryptionIface encryption;
     @Autowired
     private RandomCodeGenerator codeGenerator;
-    @Autowired
-    private FullConfiguration config;
-
-    public OAuth2ClientDto registerClient (OAuth2ClientJson clientJson,
-            String registeredBy) throws KustvaktException {
-        try {
+    
+    private void checkClientJson (OAuth2ClientJson clientJson) 
+    		throws KustvaktException {
+    	try {
             ParameterChecker.checkNameValue(clientJson.getName(),
                     "client_name");
             ParameterChecker.checkObjectValue(clientJson.getType(),
@@ -127,8 +120,53 @@
             throw new KustvaktException(StatusCodes.INVALID_REDIRECT_URI,
                     "Invalid redirect URI", OAuth2Error.INVALID_REQUEST);
         }
+	}
+    
+    private void throwRegistrationException (Exception e) throws KustvaktException {
+    	Throwable cause = e;
+        Throwable lastCause = null;
+        while ((cause = cause.getCause()) != null
+                && !cause.equals(lastCause)) {
+            if (cause instanceof SQLException) {
+                break;
+            }
+            lastCause = cause;
+        }
+        throw new KustvaktException(StatusCodes.CLIENT_REGISTRATION_FAILED,
+                cause.getMessage(), OAuth2Error.INVALID_REQUEST);
+	}
+    
+    public void registerExistingClient (OAuth2ClientJson clientJson,
+            String registeredBy, boolean isSuper, String clientId, 
+            String clientSecret) throws KustvaktException {
+    	ParameterChecker.checkStringValue(clientId,
+                "client_id");
+    	ParameterChecker.checkStringValue(clientSecret,
+                "client_secret");
+    	
+    	checkClientJson(clientJson);
+    	
+    	try {
+			clientDao.registerClient(isSuper, clientId, clientSecret,
+					clientJson.getName(), clientJson.getType(),
+					clientJson.getUrl(), clientJson.getRedirectURI(),
+					registeredBy, clientJson.getDescription(),
+					clientJson.getRefreshTokenExpiry(), clientJson.getSource());
+        }
+        catch (KustvaktException e) {
+            throw new KustvaktException(e.getStatusCode(), e.getMessage(),
+                    OAuth2Error.INVALID_REQUEST);
+        }
+        catch (Exception e) {
+            throwRegistrationException(e);
+        }
+    	
+    }
 
-        // boolean isNative = isNativeClient(url, redirectURI);
+    public OAuth2ClientDto registerClient (OAuth2ClientJson clientJson,
+            String registeredBy, boolean isSuper) throws KustvaktException {
+        
+    	checkClientJson(clientJson);
 
         String secret = null;
         String secretHashcode = null;
@@ -153,70 +191,61 @@
         id = codeGenerator.filterRandomCode(id);
 
         try {
-            clientDao.registerClient(id, secretHashcode, clientJson.getName(),
-                    clientJson.getType(), url, redirectURI, registeredBy,
-                    clientJson.getDescription(),
-                    clientJson.getRefreshTokenExpiry(), clientJson.getSource());
+			clientDao.registerClient(isSuper, id, secretHashcode,
+					clientJson.getName(), clientJson.getType(),
+					clientJson.getUrl(), clientJson.getRedirectURI(),
+					registeredBy, clientJson.getDescription(),
+					clientJson.getRefreshTokenExpiry(), clientJson.getSource());
         }
         catch (KustvaktException e) {
             throw new KustvaktException(e.getStatusCode(), e.getMessage(),
                     OAuth2Error.INVALID_REQUEST);
         }
         catch (Exception e) {
-            Throwable cause = e;
-            Throwable lastCause = null;
-            while ((cause = cause.getCause()) != null
-                    && !cause.equals(lastCause)) {
-                if (cause instanceof SQLException) {
-                    break;
-                }
-                lastCause = cause;
-            }
-            throw new KustvaktException(StatusCodes.CLIENT_REGISTRATION_FAILED,
-                    cause.getMessage(), OAuth2Error.INVALID_REQUEST);
+            throwRegistrationException(e);
         }
 
         return new OAuth2ClientDto(id, secret);
     }
 
-    @Deprecated
-    private boolean isNativeClient (String url, String redirectURI)
-            throws KustvaktException {
-        if (url == null || url.isEmpty() || redirectURI == null
-                || redirectURI.isEmpty()) {
-            return false;
-        }
-
-        String nativeHost = config.getNativeClientHost();
-        String urlHost = null;
-        try {
-            urlHost = new URL(url).getHost();
-        }
-        catch (MalformedURLException e) {
-            throw new KustvaktException(StatusCodes.INVALID_ARGUMENT,
-                    "Invalid url :" + e.getMessage(),
-                    OAuth2Error.INVALID_REQUEST);
-        }
-
-        if (!urlHost.equals(nativeHost)) {
-            return false;
-        }
-
-        String uriHost = null;
-        try {
-            uriHost = new URI(redirectURI).getHost();
-        }
-        catch (URISyntaxException e) {
-            throw new KustvaktException(StatusCodes.INVALID_ARGUMENT,
-                    "Invalid redirectURI: " + e.getMessage(),
-                    OAuth2Error.INVALID_REQUEST);
-        }
-        if (!uriHost.equals(nativeHost)) {
-            return false;
-        }
-
-        return true;
-    }
+//    @Deprecated
+//    private boolean isNativeClient (String url, String redirectURI)
+//            throws KustvaktException {
+//        if (url == null || url.isEmpty() || redirectURI == null
+//                || redirectURI.isEmpty()) {
+//            return false;
+//        }
+//
+//        String nativeHost = config.getNativeClientHost();
+//        String urlHost = null;
+//        try {
+//            urlHost = new URL(url).getHost();
+//        }
+//        catch (MalformedURLException e) {
+//            throw new KustvaktException(StatusCodes.INVALID_ARGUMENT,
+//                    "Invalid url :" + e.getMessage(),
+//                    OAuth2Error.INVALID_REQUEST);
+//        }
+//
+//        if (!urlHost.equals(nativeHost)) {
+//            return false;
+//        }
+//
+//        String uriHost = null;
+//        try {
+//            uriHost = new URI(redirectURI).getHost();
+//        }
+//        catch (URISyntaxException e) {
+//            throw new KustvaktException(StatusCodes.INVALID_ARGUMENT,
+//                    "Invalid redirectURI: " + e.getMessage(),
+//                    OAuth2Error.INVALID_REQUEST);
+//        }
+//        if (!uriHost.equals(nativeHost)) {
+//            return false;
+//        }
+//
+//        return true;
+//    }
 
     public void deregisterClient (String clientId, String username)
             throws KustvaktException {
diff --git a/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2InitClientService.java b/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2InitClientService.java
index 535ded0..4745bc6 100644
--- a/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2InitClientService.java
+++ b/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2InitClientService.java
@@ -16,7 +16,6 @@
 import de.ids_mannheim.korap.interfaces.EncryptionIface;
 import de.ids_mannheim.korap.oauth2.dao.OAuth2ClientDao;
 import de.ids_mannheim.korap.oauth2.dto.OAuth2ClientDto;
-import de.ids_mannheim.korap.oauth2.entity.OAuth2Client;
 import de.ids_mannheim.korap.utils.JsonUtils;
 import de.ids_mannheim.korap.web.input.OAuth2ClientJson;
 
@@ -50,11 +49,7 @@
         if (!f.exists()) {
             OAuth2ClientJson json = readOAuth2ClientJsonFile();
             OAuth2ClientDto clientDto = clientService.registerClient(json,
-                    "system");
-            String clientId = clientDto.getClient_id();
-            OAuth2Client client = clientService.retrieveClient(clientId);
-            client.setSuper(true);
-            clientDao.updateClient(client);
+                    "system",true);
             JsonUtils.writeFile(path, clientDto);
 
             log.info(
@@ -76,14 +71,8 @@
                 log.info("Super client info file exists but the client "
                         + "doesn't exist in the database.");
                 OAuth2ClientJson json = readOAuth2ClientJsonFile();
-                OAuth2ClientDto clientDto = clientService.registerClient(json,
-                        "system");
-                String clientId = clientDto.getClient_id();
-                OAuth2Client client = clientService.retrieveClient(clientId);
-                client.setSuper(true);
-                client.setId(existingClientId);
-                client.setSecret(secretHashcode);
-                clientDao.updateClient(client);
+                clientService.registerExistingClient(json,
+                        "system", true, existingClientId, secretHashcode);
             }
         }
     }
diff --git a/src/main/java/de/ids_mannheim/korap/web/controller/OAuthClientController.java b/src/main/java/de/ids_mannheim/korap/web/controller/OAuthClientController.java
index c0dcd8f..58a08fc 100644
--- a/src/main/java/de/ids_mannheim/korap/web/controller/OAuthClientController.java
+++ b/src/main/java/de/ids_mannheim/korap/web/controller/OAuthClientController.java
@@ -103,7 +103,7 @@
         try {
             scopeService.verifyScope(context, OAuth2Scope.REGISTER_CLIENT);
             return clientService.registerClient(clientJson,
-                    context.getUsername());
+                    context.getUsername(),false);
         }
         catch (KustvaktException e) {
             throw responseHandler.throwit(e);
diff --git a/src/test/java/de/ids_mannheim/korap/web/InitialSuperClientTest.java b/src/test/java/de/ids_mannheim/korap/web/InitialSuperClientTest.java
index afa723d..2649a77 100644
--- a/src/test/java/de/ids_mannheim/korap/web/InitialSuperClientTest.java
+++ b/src/test/java/de/ids_mannheim/korap/web/InitialSuperClientTest.java
@@ -25,17 +25,19 @@
 
     @Autowired
     private FullConfiguration config;
-
     @Autowired
     private OAuth2ClientDao clientDao;
+    @Autowired
+	private OAuth2InitClientService clientService;
 
     private String path = KustvaktConfiguration.DATA_FOLDER + "/"
             + OAuth2InitClientService.TEST_OUTPUT_FILENAME;
-
+    
     @Test
     public void testCreatingInitialSuperClient ()
             throws IOException, KustvaktException {
-        assertTrue(config.createInitialSuperClient());
+    	assertTrue(config.createInitialSuperClient());
+    	// The file was created during server start
         File f = new File(path);
         assertTrue(f.exists());
         JsonNode node = JsonUtils.readFile(path, JsonNode.class);
@@ -44,6 +46,27 @@
         OAuth2Client superClient = clientDao.retrieveClientById(superClientId);
         assertTrue(superClient.isSuper());
         testLogin(superClientId, superClientSecret);
+        assertEquals(2,clientDao.retrieveSuperClients());
+        
+        clientDao.deregisterClient(superClient);
+        assertEquals(1,clientDao.retrieveSuperClients());
+        
+        testRegisterFromExistingFile();
+    }
+    
+    private void testRegisterFromExistingFile ()
+            throws IOException, KustvaktException {
+    	
+    	clientService.createInitialTestSuperClient();
+        assertEquals(2,clientDao.retrieveSuperClients());
+        
+        JsonNode node = JsonUtils.readFile(path, JsonNode.class);
+        String superClientId = node.at("/client_id").asText();
+        OAuth2Client superClient = clientDao.retrieveClientById(superClientId);
+        assertTrue(superClient.isSuper());
+
+        clientDao.deregisterClient(superClient);
+        assertEquals(1,clientDao.retrieveSuperClients());
         removeSuperClientFile();
     }
 
diff --git a/src/test/java/de/ids_mannheim/korap/web/controller/oauth2/OAuth2TestBase.java b/src/test/java/de/ids_mannheim/korap/web/controller/oauth2/OAuth2TestBase.java
index e8d5b94..6e10946 100644
--- a/src/test/java/de/ids_mannheim/korap/web/controller/oauth2/OAuth2TestBase.java
+++ b/src/test/java/de/ids_mannheim/korap/web/controller/oauth2/OAuth2TestBase.java
@@ -100,14 +100,14 @@
 					"super confidential client", OAuth2ClientType.CONFIDENTIAL,
 					"http://korap.ids-mannheim.de/confidential",
 					"https://korap.ids-mannheim.de/confidential/redirect",
-					"system", "Super confidential client.", 0, null, false);
+					"system", "Super confidential client.", 0, null);
 		}
 		
 		try {
 			clientDao.retrieveClientById(publicClientId);
 		}
 		catch (KustvaktException e) {
-			clientDao.registerClient(publicClientId, null,
+			clientDao.registerClient(false, publicClientId, null,
 					"public client plugin with redirect uri",
 					OAuth2ClientType.PUBLIC, "https://third.party.client.com",
 					"https://third.party.client.com/redirect", "system",
@@ -119,7 +119,7 @@
 			clientDao.retrieveClientById(publicClientId2);
 		}
 		catch (KustvaktException e) {
-			clientDao.registerClient(publicClientId2, null,
+			clientDao.registerClient(false, publicClientId2, null,
 					"test public client", OAuth2ClientType.PUBLIC,
 					"http://korap.ids-mannheim.de/public", null, "system",
 					"Public client without redirect uri", 0, null);
@@ -129,7 +129,7 @@
 			clientDao.retrieveClientById(confidentialClientId);
 		}
 		catch (KustvaktException e) {
-			clientDao.registerClient(confidentialClientId,
+			clientDao.registerClient(false, confidentialClientId,
 					"$2a$08$vi1FbuN3p6GcI1tSxMAoeuIYL8Yw3j6A8wJthaN8ZboVnrQaTwLPq",
 					"non super confidential client",
 					OAuth2ClientType.CONFIDENTIAL,
@@ -148,7 +148,10 @@
 					"confidential client 2", OAuth2ClientType.CONFIDENTIAL,
 					"http://example.client.de", null, "system",
 					"Nonsuper confidential client plugin without redirect URI",
-					0, source, true);
+					0, source);
+			OAuth2Client client = clientDao.retrieveClientById(confidentialClientId2);
+			client.setPermitted(true);
+			clientDao.updateClient(client);
 		}
 	}
     
diff --git a/src/test/resources/test-jdbc.properties b/src/test/resources/test-jdbc.properties
index 5e84ae0..4489537 100644
--- a/src/test/resources/test-jdbc.properties
+++ b/src/test/resources/test-jdbc.properties
@@ -5,7 +5,7 @@
 jdbc.driverClassName=org.sqlite.JDBC
 #jdbc.url=jdbc:sqlite::memory:
 jdbc.url=jdbc:sqlite:file::memory:?cache=shared
-#jdbc.url=jdbc:sqlite:testDB.sqlite
+#jdbc.url=jdbc:sqlite:data/testDB.sqlite
 jdbc.username=pc
 jdbc.password=pc
 jdbc.schemaPath=classpath:db/sqlite,db/predefined
\ No newline at end of file