diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/CanonicalConstantNaming.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/CanonicalConstantNaming.java
index f95755edcb..0e5afd8d9c 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/CanonicalConstantNaming.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/CanonicalConstantNaming.java
@@ -127,7 +127,7 @@ private static ImmutableList<VariableTree> getVariablesInCompilationUnit(
       @Override
       public @Nullable Void visitVariable(VariableTree variableTree, @Nullable Void unused) {
         variablesInFileBuilder.add(variableTree);
-        return super.visitVariable(variableTree, unused);
+        return super.visitVariable(variableTree, null);
       }
     }.scan(tree, null);