diff --git a/webapi/src/main/scala/org/knora/webapi/slice/admin/domain/model/KnoraGroup.scala b/webapi/src/main/scala/org/knora/webapi/slice/admin/domain/model/KnoraGroup.scala
index cc81e74d1f..0ecdc83cdd 100644
--- a/webapi/src/main/scala/org/knora/webapi/slice/admin/domain/model/KnoraGroup.scala
+++ b/webapi/src/main/scala/org/knora/webapi/slice/admin/domain/model/KnoraGroup.scala
@@ -105,7 +105,7 @@ object GroupIri extends StringValueCompanion[GroupIri] {
   def from(value: String): Either[String, GroupIri] = value match {
     case _ if value.isEmpty          => Left("Group IRI cannot be empty.")
     case _ if isGroupIriValid(value) => Right(GroupIri(value))
-    case _                           => Left("Group IRI is invalid.")
+    case v                           => Left(s"Group IRI is invalid: $v")
   }
 
   /**