diff --git a/cookbook/src/main/java/com/fluxtion/example/cookbook/ml/linearregression/api/OpportunityNotifier.java b/cookbook/src/main/java/com/fluxtion/example/cookbook/ml/linearregression/api/OpportunityNotifier.java
index e6d8141..5a633d7 100644
--- a/cookbook/src/main/java/com/fluxtion/example/cookbook/ml/linearregression/api/OpportunityNotifier.java
+++ b/cookbook/src/main/java/com/fluxtion/example/cookbook/ml/linearregression/api/OpportunityNotifier.java
@@ -3,7 +3,7 @@
 import java.util.function.Consumer;
 
 public interface OpportunityNotifier {
-    default void setNotificationSink(Consumer<Object> notifierSink){}
-    default void setProfitTrigger(double profitTrigger){}
-    default void setEnableNotifications(boolean enableNotifications){}
+    void setNotificationSink(Consumer<Object> notifierSink);
+    void setProfitTrigger(double profitTrigger);
+    void setEnableNotifications(boolean enableNotifications);
 }