diff --git a/AFNetworking/AFImageRequestOperation.m b/AFNetworking/AFImageRequestOperation.m
index 7fb166d..0a0390f 100644
--- a/AFNetworking/AFImageRequestOperation.m
+++ b/AFNetworking/AFImageRequestOperation.m
@@ -22,11 +22,12 @@
 
 #import "AFImageRequestOperation.h"
 
-static dispatch_queue_t af_image_request_operation_processing_queue;
 static dispatch_queue_t image_request_operation_processing_queue() {
-    if (af_image_request_operation_processing_queue == NULL) {
+    static dispatch_queue_t af_image_request_operation_processing_queue;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
         af_image_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.image-request.processing", DISPATCH_QUEUE_CONCURRENT);
-    }
+    });
 
     return af_image_request_operation_processing_queue;
 }
diff --git a/AFNetworking/AFJSONRequestOperation.m b/AFNetworking/AFJSONRequestOperation.m
index 3d713b7..008aacc 100644
--- a/AFNetworking/AFJSONRequestOperation.m
+++ b/AFNetworking/AFJSONRequestOperation.m
@@ -22,11 +22,12 @@
 
 #import "AFJSONRequestOperation.h"
 
-static dispatch_queue_t af_json_request_operation_processing_queue;
 static dispatch_queue_t json_request_operation_processing_queue() {
-    if (af_json_request_operation_processing_queue == NULL) {
+    static dispatch_queue_t af_json_request_operation_processing_queue;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
         af_json_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.json-request.processing", DISPATCH_QUEUE_CONCURRENT);
-    }
+    });
 
     return af_json_request_operation_processing_queue;
 }
diff --git a/AFNetworking/AFPropertyListRequestOperation.m b/AFNetworking/AFPropertyListRequestOperation.m
index d9612f7..4d6123b 100644
--- a/AFNetworking/AFPropertyListRequestOperation.m
+++ b/AFNetworking/AFPropertyListRequestOperation.m
@@ -22,11 +22,12 @@
 
 #import "AFPropertyListRequestOperation.h"
 
-static dispatch_queue_t af_property_list_request_operation_processing_queue;
 static dispatch_queue_t property_list_request_operation_processing_queue() {
-    if (af_property_list_request_operation_processing_queue == NULL) {
+    static dispatch_queue_t af_property_list_request_operation_processing_queue;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
         af_property_list_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.property-list-request.processing", DISPATCH_QUEUE_CONCURRENT);
-    }
+    });
 
     return af_property_list_request_operation_processing_queue;
 }
diff --git a/AFNetworking/AFXMLRequestOperation.m b/AFNetworking/AFXMLRequestOperation.m
index 8ebd4ed..30a76b9 100644
--- a/AFNetworking/AFXMLRequestOperation.m
+++ b/AFNetworking/AFXMLRequestOperation.m
@@ -24,11 +24,12 @@
 
 #include <Availability.h>
 
-static dispatch_queue_t af_xml_request_operation_processing_queue;
 static dispatch_queue_t xml_request_operation_processing_queue() {
-    if (af_xml_request_operation_processing_queue == NULL) {
+    static dispatch_queue_t af_xml_request_operation_processing_queue;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
         af_xml_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.xml-request.processing", DISPATCH_QUEUE_CONCURRENT);
-    }
+    });
 
     return af_xml_request_operation_processing_queue;
 }