diff --git a/scm-core/src/main/java/sonia/scm/group/Group.java b/scm-core/src/main/java/sonia/scm/group/Group.java
index 6774d51b63..b55395c953 100644
--- a/scm-core/src/main/java/sonia/scm/group/Group.java
+++ b/scm-core/src/main/java/sonia/scm/group/Group.java
@@ -37,6 +37,7 @@ package sonia.scm.group;
 
 import sonia.scm.ModelObject;
 import sonia.scm.util.Util;
+import sonia.scm.util.ValidationUtil;
 
 //~--- JDK imports ------------------------------------------------------------
 
@@ -450,7 +451,7 @@ public class Group implements ModelObject, Iterable<String>
   @Override
   public boolean isValid()
   {
-    return Util.isNotEmpty(name) && Util.isNotEmpty(type);
+    return ValidationUtil.isNameValid(name) && Util.isNotEmpty(type);
   }
 
   //~--- set methods ----------------------------------------------------------
diff --git a/scm-core/src/main/java/sonia/scm/repository/Repository.java b/scm-core/src/main/java/sonia/scm/repository/Repository.java
index 4282de556c..4c58b044e6 100644
--- a/scm-core/src/main/java/sonia/scm/repository/Repository.java
+++ b/scm-core/src/main/java/sonia/scm/repository/Repository.java
@@ -352,6 +352,7 @@ public class Repository implements ModelObject
    *
    * @return
    */
+  @Override
   public String getId()
   {
     return id;
@@ -434,7 +435,7 @@ public class Repository implements ModelObject
   @Override
   public boolean isValid()
   {
-    return Util.isNotEmpty(name) && Util.isNotEmpty(type)
+    return ValidationUtil.isNameValid(name) && Util.isNotEmpty(type)
            && ((Util.isEmpty(contact))
                || ValidationUtil.isMailAddressValid(contact));
   }
diff --git a/scm-core/src/main/java/sonia/scm/user/User.java b/scm-core/src/main/java/sonia/scm/user/User.java
index 0e37d00c8a..58572cbbf1 100644
--- a/scm-core/src/main/java/sonia/scm/user/User.java
+++ b/scm-core/src/main/java/sonia/scm/user/User.java
@@ -418,7 +418,7 @@ public class User implements Principal, ModelObject
   @Override
   public boolean isValid()
   {
-    return Util.isNotEmpty(name) && Util.isNotEmpty(displayName)
+    return ValidationUtil.isUsernameValid(name) && Util.isNotEmpty(displayName)
            && Util.isNotEmpty(type)
            && ((Util.isEmpty(mail)) || ValidationUtil.isMailAddressValid(mail));
   }