diff --git a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/predicate/operator/arithmetic/AddTests.java b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/predicate/operator/arithmetic/AddTests.java
index 2022fe1cb1579..ae44a7a1d5cd3 100644
--- a/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/predicate/operator/arithmetic/AddTests.java
+++ b/x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/predicate/operator/arithmetic/AddTests.java
@@ -159,7 +159,7 @@ public static Iterable<Object[]> parameters() {
         };
         BiFunction<TestCaseSupplier.TypedData, TestCaseSupplier.TypedData, List<String>> warnings = (lhs, rhs) -> {
             try {
-                addDatesAndTemporalAmount(lhs.data(), rhs.data(), AddTests::addMillis);
+                addDatesAndTemporalAmount(lhs.getValue(), rhs.getValue(), AddTests::addMillis);
                 return List.of();
             } catch (ArithmeticException e) {
                 return List.of(
@@ -332,6 +332,7 @@ private static Object addDatesAndTemporalAmount(Object lhs, Object rhs, ToLongBi
         // this weird casting dance makes the expected value lambda symmetric
         Instant date;
         TemporalAmount period;
+        assert (lhs instanceof Instant) || (rhs instanceof Instant);
         if (lhs instanceof Instant) {
             date = (Instant) lhs;
             period = (TemporalAmount) rhs;