diff --git a/modules/elasticsearch/src/main/java/org/elasticsearch/action/search/SearchOperationThreading.java b/modules/elasticsearch/src/main/java/org/elasticsearch/action/search/SearchOperationThreading.java
index 1c42fb40a0e..75c40ac1495 100644
--- a/modules/elasticsearch/src/main/java/org/elasticsearch/action/search/SearchOperationThreading.java
+++ b/modules/elasticsearch/src/main/java/org/elasticsearch/action/search/SearchOperationThreading.java
@@ -20,6 +20,7 @@
 package org.elasticsearch.action.search;
 
 import org.elasticsearch.ElasticSearchIllegalArgumentException;
+import org.elasticsearch.common.Nullable;
 
 /**
  * Controls the operation threading model for search operation that are performed
@@ -65,7 +66,7 @@ public enum SearchOperationThreading {
         throw new ElasticSearchIllegalArgumentException("No type matching id [" + id + "]");
     }
 
-    public static SearchOperationThreading fromString(String value, SearchOperationThreading defaultValue) {
+    public static SearchOperationThreading fromString(String value, @Nullable SearchOperationThreading defaultValue) {
         if (value == null) {
             return defaultValue;
         }
diff --git a/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java b/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java
index 9a880b67a9f..f46cef0d81d 100644
--- a/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java
+++ b/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java
@@ -69,12 +69,14 @@ public class RestSearchAction extends BaseRestHandler {
         try {
             searchRequest = parseSearchRequest(request);
             searchRequest.listenerThreaded(false);
-            SearchOperationThreading operationThreading = SearchOperationThreading.fromString(request.param("operation_threading"), SearchOperationThreading.SINGLE_THREAD);
-            if (operationThreading == SearchOperationThreading.NO_THREADS) {
-                // since we don't spawn, don't allow no_threads, but change it to a single thread
-                operationThreading = SearchOperationThreading.SINGLE_THREAD;
+            SearchOperationThreading operationThreading = SearchOperationThreading.fromString(request.param("operation_threading"), null);
+            if (operationThreading != null) {
+                if (operationThreading == SearchOperationThreading.NO_THREADS) {
+                    // since we don't spawn, don't allow no_threads, but change it to a single thread
+                    operationThreading = SearchOperationThreading.SINGLE_THREAD;
+                }
+                searchRequest.operationThreading(operationThreading);
             }
-            searchRequest.operationThreading(operationThreading);
         } catch (Exception e) {
             if (logger.isDebugEnabled()) {
                 logger.debug("failed to parse search request parameters", e);
diff --git a/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchScrollAction.java b/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchScrollAction.java
index ef833b60e54..cead1a36827 100644
--- a/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchScrollAction.java
+++ b/modules/elasticsearch/src/main/java/org/elasticsearch/rest/action/search/RestSearchScrollAction.java
@@ -68,12 +68,14 @@ public class RestSearchScrollAction extends BaseRestHandler {
                 searchScrollRequest.scroll(new Scroll(parseTimeValue(scroll, null)));
             }
             searchScrollRequest.listenerThreaded(false);
-            SearchOperationThreading operationThreading = SearchOperationThreading.fromString(request.param("operation_threading"), SearchOperationThreading.SINGLE_THREAD);
-            if (operationThreading == SearchOperationThreading.NO_THREADS) {
-                // since we don't spawn, don't allow no_threads, but change it to a single thread
-                operationThreading = SearchOperationThreading.SINGLE_THREAD;
+            SearchOperationThreading operationThreading = SearchOperationThreading.fromString(request.param("operation_threading"), null);
+            if (operationThreading != null) {
+                if (operationThreading == SearchOperationThreading.NO_THREADS) {
+                    // since we don't spawn, don't allow no_threads, but change it to a single thread
+                    operationThreading = SearchOperationThreading.SINGLE_THREAD;
+                }
+                searchScrollRequest.operationThreading(operationThreading);
             }
-            searchScrollRequest.operationThreading(operationThreading);
         } catch (Exception e) {
             try {
                 XContentBuilder builder = restContentBuilder(request);