diff --git a/sql/src/main/java/org/apache/calcite/sql/type/CastedLiteralOperandTypeCheckers.java b/sql/src/main/java/org/apache/calcite/sql/type/CastedLiteralOperandTypeCheckers.java
index 00ea89fafc7c..0155f7ba6f45 100644
--- a/sql/src/main/java/org/apache/calcite/sql/type/CastedLiteralOperandTypeCheckers.java
+++ b/sql/src/main/java/org/apache/calcite/sql/type/CastedLiteralOperandTypeCheckers.java
@@ -34,7 +34,7 @@
 
 public class CastedLiteralOperandTypeCheckers
 {
-  public static SqlSingleOperandTypeChecker LITERAL = new CastedLiteralOperandTypeChecker(false);
+  public static final SqlSingleOperandTypeChecker LITERAL = new CastedLiteralOperandTypeChecker(false);
 
   /**
    * Blatantly copied from {@link OperandTypes#POSITIVE_INTEGER_LITERAL}, however the reference to the {@link #LITERAL}