diff --git a/full/Changes b/full/Changes
index 7d19904..9f8e800 100644
--- a/full/Changes
+++ b/full/Changes
@@ -1,7 +1,8 @@
 # version 0.63.2
 2021-06-11
  - Updated OAuth2 token length & secure random algorithm config.
-
+ - Added character set filter to random code generator, e.g. for client_id.
+ 
 # version 0.63.1
 2021-02-22
  - Updated libraries (margaretha)
diff --git a/full/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java b/full/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
index 7328c81..0180c27 100644
--- a/full/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
+++ b/full/src/main/java/de/ids_mannheim/korap/oauth2/service/OAuth2ClientService.java
@@ -126,6 +126,7 @@
         }
 
         String id = codeGenerator.createRandomCode();
+        id = codeGenerator.filterRandomCode(id);
         try {
             clientDao.registerClient(id, secretHashcode, clientJson.getName(),
                     clientJson.getType(), url, redirectURI, registeredBy,
diff --git a/full/src/test/java/de/ids_mannheim/korap/authentication/RandomCodeGeneratorTest.java b/full/src/test/java/de/ids_mannheim/korap/authentication/RandomCodeGeneratorTest.java
index 6097cd2..952f804 100644
--- a/full/src/test/java/de/ids_mannheim/korap/authentication/RandomCodeGeneratorTest.java
+++ b/full/src/test/java/de/ids_mannheim/korap/authentication/RandomCodeGeneratorTest.java
@@ -6,6 +6,7 @@
 
 import org.apache.oltu.oauth2.as.issuer.MD5Generator;
 import org.apache.oltu.oauth2.common.exception.OAuthSystemException;
+import org.junit.Ignore;
 import org.junit.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 
@@ -26,14 +27,17 @@
         //System.out.println(value);
     }
 
+    @Ignore
     public void testRandomGeneratorPerformance () throws OAuthSystemException,
             NoSuchAlgorithmException, KustvaktException {
         long min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
 
+        String code;
         while (true) {
             long start = System.currentTimeMillis();
             for (int i = 0; i < 10000; i++) {
-                random.createRandomCode();
+                code = random.createRandomCode();
+                code = random.filterRandomCode(code);
             }
             long end = System.currentTimeMillis();
             long duration = end - start;
@@ -46,6 +50,7 @@
         }
     }
 
+    @Ignore
     public void testMD5Generator () throws OAuthSystemException,
             NoSuchAlgorithmException, KustvaktException {
         MD5Generator m = new MD5Generator();
diff --git a/full/src/test/java/de/ids_mannheim/korap/web/controller/OAuth2ClientControllerTest.java b/full/src/test/java/de/ids_mannheim/korap/web/controller/OAuth2ClientControllerTest.java
index a0d0f88..a232d43 100644
--- a/full/src/test/java/de/ids_mannheim/korap/web/controller/OAuth2ClientControllerTest.java
+++ b/full/src/test/java/de/ids_mannheim/korap/web/controller/OAuth2ClientControllerTest.java
@@ -141,6 +141,8 @@
         assertNotNull(clientId);
         assertNotNull(clientSecret);
 
+        assertFalse(clientId.contains("a"));
+            
         testResetConfidentialClientSecret(clientId, clientSecret);
         testDeregisterConfidentialClient(clientId);
     }
diff --git a/full/src/test/resources/kustvakt-test.conf b/full/src/test/resources/kustvakt-test.conf
index 512ef34..bc6f8e3 100644
--- a/full/src/test/resources/kustvakt-test.conf
+++ b/full/src/test/resources/kustvakt-test.conf
@@ -62,7 +62,7 @@
 oauth2.refresh.token.expiry = 90D
 oauth2.authorization.code.expiry = 10M
 # -- scopes separated by space
-oauth2.default.scopes = openid search match_info
+oauth2.default.scopes = search match_info
 oauth2.client.credentials.scopes = client_info
 
 ## OpenId