diff --git a/src/main/java/org/apache/maven/plugins/jlink/AbstractJLinkMojo.java b/src/main/java/org/apache/maven/plugins/jlink/AbstractJLinkMojo.java
index d195559..6a590a3 100644
--- a/src/main/java/org/apache/maven/plugins/jlink/AbstractJLinkMojo.java
+++ b/src/main/java/org/apache/maven/plugins/jlink/AbstractJLinkMojo.java
@@ -71,7 +71,7 @@ public abstract class AbstractJLinkMojo extends AbstractMojo {
     @Parameter(defaultValue = "${session}", readonly = true, required = true)
     private MavenSession session;
 
-    private ToolchainManager toolchainManager;
+    private final ToolchainManager toolchainManager;
 
     public AbstractJLinkMojo(ToolchainManager toolchainManager) {
         this.toolchainManager = toolchainManager;