diff --git a/src/main/java/net/logstash/logback/composite/loggingevent/AbstractThrowableClassNameJsonProvider.java b/src/main/java/net/logstash/logback/composite/loggingevent/AbstractThrowableClassNameJsonProvider.java
index 0199c13c..45949cba 100644
--- a/src/main/java/net/logstash/logback/composite/loggingevent/AbstractThrowableClassNameJsonProvider.java
+++ b/src/main/java/net/logstash/logback/composite/loggingevent/AbstractThrowableClassNameJsonProvider.java
@@ -57,7 +57,7 @@ private String determineClassName(IThrowableProxy throwable) {
     /**
      * @return null if no appropriate throwable
      */
-    abstract IThrowableProxy getThrowable(IThrowableProxy throwable);
+    protected abstract IThrowableProxy getThrowable(IThrowableProxy throwable);
 
     public void setUseSimpleClassName(boolean useSimpleClassName) {
         this.useSimpleClassName = useSimpleClassName;
diff --git a/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableClassNameJsonProvider.java b/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableClassNameJsonProvider.java
index 45196128..f9664591 100644
--- a/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableClassNameJsonProvider.java
+++ b/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableClassNameJsonProvider.java
@@ -25,7 +25,7 @@ public ThrowableClassNameJsonProvider() {
     }
 
     @Override
-    IThrowableProxy getThrowable(IThrowableProxy throwable) {
+    protected IThrowableProxy getThrowable(IThrowableProxy throwable) {
         return throwable;
     }
 }
diff --git a/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableRootCauseClassNameJsonProvider.java b/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableRootCauseClassNameJsonProvider.java
index a5b523b7..1bddd486 100644
--- a/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableRootCauseClassNameJsonProvider.java
+++ b/src/main/java/net/logstash/logback/composite/loggingevent/ThrowableRootCauseClassNameJsonProvider.java
@@ -30,7 +30,7 @@ public ThrowableRootCauseClassNameJsonProvider() {
     }
 
     @Override
-    IThrowableProxy getThrowable(IThrowableProxy throwable) {
+    protected IThrowableProxy getThrowable(IThrowableProxy throwable) {
         return throwable == null ? null : ThrowableSelectors.rootCause(throwable);
     }
 }