diff --git a/src/main/java/edu/group5/app/model/user/Customer.java b/src/main/java/edu/group5/app/model/user/Customer.java
index ab7bcd2..4f52b19 100644
--- a/src/main/java/edu/group5/app/model/user/Customer.java
+++ b/src/main/java/edu/group5/app/model/user/Customer.java
@@ -37,7 +37,7 @@ public List<Integer> getPreferences() {
   }
 
   public void addPreference(int orgNumber) {
-    if (!preferences.contains(orgNumber)) {
+    if (preferences.contains(orgNumber)) {
       throw new IllegalArgumentException("Organization number already in preferences");
     }
     preferences.add(orgNumber);