diff --git a/obp-api/src/main/scala/code/api/util/APIUtil.scala b/obp-api/src/main/scala/code/api/util/APIUtil.scala
index beb874d86..1aaf4f3f4 100644
--- a/obp-api/src/main/scala/code/api/util/APIUtil.scala
+++ b/obp-api/src/main/scala/code/api/util/APIUtil.scala
@@ -900,7 +900,7 @@ object APIUtil extends MdcLoggable with CustomJsonFormats{
     }
   }
 
-  /** only  A-Z, a-z, 0-9, -, _, ., and max length <= 16  */
+  /** only  A-Z, a-z, 0-9, -, _, ., and max length <= 16. NOTE: This function requires at least ONE character (+ in the regx). If you want to accept zero characters use checkOptionalShortString.  */
   def checkShortString(value:String): String ={
     val valueLength = value.length
     val regex = """^([A-Za-z0-9\-._]+)$""".r