diff --git a/modules/aggs-matrix-stats/src/test/java/org/elasticsearch/search/aggregations/matrix/stats/InternalMatrixStatsTests.java b/modules/aggs-matrix-stats/src/test/java/org/elasticsearch/search/aggregations/matrix/stats/InternalMatrixStatsTests.java
index 69e14c14a7c..6ff132b32fa 100644
--- a/modules/aggs-matrix-stats/src/test/java/org/elasticsearch/search/aggregations/matrix/stats/InternalMatrixStatsTests.java
+++ b/modules/aggs-matrix-stats/src/test/java/org/elasticsearch/search/aggregations/matrix/stats/InternalMatrixStatsTests.java
@@ -193,7 +193,7 @@ public class InternalMatrixStatsTests extends InternalAggregationTestCase<Intern
         }
 
         final String unknownField = randomAlphaOfLength(3);
-        final String other = randomAlphaOfLength(3);
+        final String other = randomValueOtherThan(unknownField, () -> randomAlphaOfLength(3));
 
         for (MatrixStats matrix : Arrays.asList(actual)) {