diff --git a/docs/changelog/135945.yaml b/docs/changelog/135945.yaml
new file mode 100644
index 0000000000000..88b99bce10274
--- /dev/null
+++ b/docs/changelog/135945.yaml
@@ -0,0 +1,5 @@
+pr: 135945
+summary: OOB fix in reranker constructing object parsing
+area: Relevance
+type: bug
+issues: []
diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/rank/textsimilarity/TextSimilarityRankRetrieverBuilder.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/rank/textsimilarity/TextSimilarityRankRetrieverBuilder.java
index d45a93c1444e3..9769a4a1c8a21 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/rank/textsimilarity/TextSimilarityRankRetrieverBuilder.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/rank/textsimilarity/TextSimilarityRankRetrieverBuilder.java
@@ -79,9 +79,9 @@ public class TextSimilarityRankRetrieverBuilder extends CompoundRetrieverBuilder
 
     private static final ConstructingObjectParser<ChunkScorerConfig, RetrieverParserContext> CHUNK_SCORER_PARSER =
         new ConstructingObjectParser<>(CHUNK_RESCORER_FIELD.getPreferredName(), true, args -> {
-            Integer size = (Integer) args[0];
+            Integer size = args.size > 0 ? (Integer) args[0] : null;
             @SuppressWarnings("unchecked")
-            Map<String, Object> chunkingSettingsMap = (Map<String, Object>) args[1];
+            Map<String, Object> chunkingSettingsMap = args.size > 1 ? (Map<String, Object>) args[1] : null;
             ChunkingSettings chunkingSettings = ChunkScorerConfig.chunkingSettingsFromMap(chunkingSettingsMap);
             return new ChunkScorerConfig(size, chunkingSettings);
         });