diff --git a/src/main/java/DNPM/dto/Studie.java b/src/main/java/DNPM/dto/Studie.java
index 601576a..59d3cfe 100644
--- a/src/main/java/DNPM/dto/Studie.java
+++ b/src/main/java/DNPM/dto/Studie.java
@@ -63,7 +63,7 @@ public class Studie {
     }
 
     private boolean hasEudraCtNumber() {
-        return null != studiennummer && studiennummer.matches("[0-9]{4}-[0-9]{6}-[0-9]{2}");
+        return null != studiennummer && studiennummer.matches("\\d{4}-\\d{6}-\\d{2}");
     }
 
     public enum Type {