diff --git a/java-checks/src/main/java/org/sonar/java/checks/design/AbstractCouplingChecker.java b/java-checks/src/main/java/org/sonar/java/checks/design/AbstractCouplingChecker.java
index de061f354df..2a22f993bf4 100644
--- a/java-checks/src/main/java/org/sonar/java/checks/design/AbstractCouplingChecker.java
+++ b/java-checks/src/main/java/org/sonar/java/checks/design/AbstractCouplingChecker.java
@@ -49,7 +49,7 @@ public abstract class AbstractCouplingChecker extends BaseTreeVisitor implements
   /**
    * Implementations of this method should add the fully-qualified name of the type to the set {@link AbstractCouplingChecker#types}.
    */
-  abstract void checkTypes(@Nullable Tree type, Set<String> types);
+  abstract void checkTypes(@Nullable Tree type, @Nullable Set<String> types);
 
   @Override
   public void scanFile(JavaFileScannerContext context) {