diff --git a/server/src/main/java/org/elasticsearch/search/retriever/CompoundRetrieverBuilder.java b/server/src/main/java/org/elasticsearch/search/retriever/CompoundRetrieverBuilder.java
index 0527179d42b73..cedbf9e1e75c3 100644
--- a/server/src/main/java/org/elasticsearch/search/retriever/CompoundRetrieverBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/retriever/CompoundRetrieverBuilder.java
@@ -233,15 +233,17 @@ public ActionRequestValidationException validate(
         for (RetrieverSource innerRetriever : innerRetrievers) {
             validationException = innerRetriever.retriever().validate(source, validationException, isScroll, allowPartialSearchResults);
             if (innerRetriever.retriever() instanceof CompoundRetrieverBuilder<?> compoundChild) {
-                String errorMessage = String.format(
-                    Locale.ROOT,
-                    "[%s] requires [rank_window_size: %d] to be smaller than or equal to its sub retriever's %s [rank_window_size: %d]",
-                    this.getName(),
-                    rankWindowSize,
-                    compoundChild.getName(),
-                    compoundChild.rankWindowSize
-                );
-                validationException = addValidationError(errorMessage, validationException);
+                if (rankWindowSize > compoundChild.rankWindowSize) {
+                    String errorMessage = String.format(
+                            Locale.ROOT,
+                            "[%s] requires [rank_window_size: %d] to be smaller than or equal to its sub retriever's %s [rank_window_size: %d]",
+                            this.getName(),
+                            rankWindowSize,
+                            compoundChild.getName(),
+                            compoundChild.rankWindowSize
+                    );
+                    validationException = addValidationError(errorMessage, validationException);
+                }
             }
         }
         return validationException;