diff --git a/scrapy/utils/queue.py b/scrapy/utils/queue.py
index fe6e9c75f..35fa9102c 100644
--- a/scrapy/utils/queue.py
+++ b/scrapy/utils/queue.py
@@ -10,13 +10,11 @@ class FifoMemoryQueue(object):
 
     def __init__(self):
         self.q = deque()
-
-    def push(self, obj):
-        self.q.appendleft(obj)
+        self.push = self.q.append
 
     def pop(self):
-        if self.q:
-            return self.q.pop()
+        q = self.q
+        return q.popleft() if q else None
 
     def close(self):
         pass
@@ -28,8 +26,9 @@ class FifoMemoryQueue(object):
 class LifoMemoryQueue(FifoMemoryQueue):
     """Memory LIFO queue."""
 
-    def push(self, obj):
-        self.q.append(obj)
+    def pop(self):
+        q = self.q
+        return q.pop() if q else None
 
 
 class FifoDiskQueue(object):