diff --git a/a8/orderbuffer.cc b/a8/orderbuffer.cc
index 0b9f60b..5cb27a0 100644
--- a/a8/orderbuffer.cc
+++ b/a8/orderbuffer.cc
@@ -5,7 +5,7 @@
 namespace a8
 {
 
-    OrderBuffer::OrderBuffer(int buf_len)
+    OrderBuffer::OrderBuffer(unsigned int buf_len)
     {
         if (buf_len <= 0) {
             abort();
@@ -21,12 +21,12 @@ namespace a8
         buf_len_ = 0;
     }
 
-    char* OrderBuffer::Alloc(int len)
+    char* OrderBuffer::Alloc(unsigned int len)
     {
         if (len <= 0) {
             abort();
         }
-        int real_len = len + 4;
+        unsigned int real_len = len + 4;
     }
 
     void OrderBuffer::Free(char* p)
diff --git a/a8/orderbuffer.h b/a8/orderbuffer.h
index eb87d94..4193f67 100644
--- a/a8/orderbuffer.h
+++ b/a8/orderbuffer.h
@@ -9,18 +9,18 @@ namespace a8
     {
     public:
 
-        OrderBuffer(int buf_len);
+        OrderBuffer(unsigned int buf_len);
         ~OrderBuffer();
 
-        char* Alloc(int len);
+        char* Alloc(unsigned int len);
         void Free(char* p);
 
     private:
 
         char* buf_ = nullptr;
-        int buf_len_ = 0;
-        std::atomic<int> start_ = 0;
-        std::atomic<int> end_ = 0;
+        unsigned int buf_len_ = 0;
+        std::atomic<unsigned int> start_ = 0;
+        std::atomic<unsigned int> end_ = 0;
 
     };