diff --git a/core/src/main/java/org/apache/commons/proxy2/invoker/recorder/InvocationRecorder.java b/core/src/main/java/org/apache/commons/proxy2/invoker/recorder/InvocationRecorder.java
index f170db0..ca56bdd 100644
--- a/core/src/main/java/org/apache/commons/proxy2/invoker/recorder/InvocationRecorder.java
+++ b/core/src/main/java/org/apache/commons/proxy2/invoker/recorder/InvocationRecorder.java
@@ -36,7 +36,7 @@
 public class InvocationRecorder
 {
     private final ProxyFactory proxyFactory;
-    private List<RecordedInvocation> recordedInvocations = new LinkedList<RecordedInvocation>();
+    private final List<RecordedInvocation> recordedInvocations = new LinkedList<RecordedInvocation>();
 
     /**
      * Create a new InvocationRecorder instance.
diff --git a/core/src/main/java/org/apache/commons/proxy2/stub/TrainingContext.java b/core/src/main/java/org/apache/commons/proxy2/stub/TrainingContext.java
index 328f1a0..d9904d3 100644
--- a/core/src/main/java/org/apache/commons/proxy2/stub/TrainingContext.java
+++ b/core/src/main/java/org/apache/commons/proxy2/stub/TrainingContext.java
@@ -46,7 +46,7 @@
 
     private final ProxyFactory proxyFactory;
 
-    private Deque<TrainingContextFrame<?>> frameDeque = new LinkedList<TrainingContextFrame<?>>();
+    private final Deque<TrainingContextFrame<?>> frameDeque = new LinkedList<TrainingContextFrame<?>>();
 
     private final TrainingContext resume;