diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ltr/QueryExtractorBuilder.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ltr/QueryExtractorBuilder.java
index e6d20c845c222..4bbe92c6cc769 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ltr/QueryExtractorBuilder.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/trainedmodel/ltr/QueryExtractorBuilder.java
@@ -70,6 +70,9 @@ public QueryExtractorBuilder(String featureName, QueryProvider query) {
     public QueryExtractorBuilder(String featureName, QueryProvider query, float defaultScore) {
         this.featureName = requireNonNull(featureName, FEATURE_NAME);
         this.query = requireNonNull(query, QUERY);
+        if (defaultScore < 0f) {
+            throw new IllegalArgumentException("[" + NAME + "] requires defaultScore to be positive.");
+        }
         this.defaultScore = defaultScore;
     }