diff --git a/RFS/src/main/java/org/opensearch/migrations/bulkload/common/InvalidResponse.java b/RFS/src/main/java/org/opensearch/migrations/bulkload/common/InvalidResponse.java
index 33973afd4..2205a99c5 100644
--- a/RFS/src/main/java/org/opensearch/migrations/bulkload/common/InvalidResponse.java
+++ b/RFS/src/main/java/org/opensearch/migrations/bulkload/common/InvalidResponse.java
@@ -17,7 +17,7 @@
 
 @Slf4j
 public class InvalidResponse extends RfsException {
-    private static final Pattern UNKNOWN_SETTING = Pattern.compile("unknown setting \\[(.+?)\\].+");
+    private static final Pattern UNKNOWN_SETTING = Pattern.compile("unknown setting \\[([a-zA-Z0-9_.-]+)\\].+");
     private static final ObjectMapper objectMapper = new ObjectMapper();
     private final transient HttpResponse response;