diff --git a/muduo/base/Date.h b/muduo/base/Date.h
index 2e27b19cd..0379144d5 100644
--- a/muduo/base/Date.h
+++ b/muduo/base/Date.h
@@ -33,7 +33,7 @@ class Date : public muduo::copyable
     int day;  // [1..31]
   };
 
-  static const int kDaysPerWeek = 7;
+  static constexpr int kDaysPerWeek = 7;
   static const int kJulianDayOf1970_01_01;
 
   ///
diff --git a/muduo/net/Buffer.h b/muduo/net/Buffer.h
index 4fa82d4bd..2975c05c4 100644
--- a/muduo/net/Buffer.h
+++ b/muduo/net/Buffer.h
@@ -42,8 +42,8 @@ namespace net
 class Buffer : public muduo::copyable
 {
  public:
-  static const size_t kCheapPrepend = 8;
-  static const size_t kInitialSize = 1024;
+  static constexpr size_t kCheapPrepend = 8;
+  static constexpr size_t kInitialSize = 1024;
 
   explicit Buffer(size_t initialSize = kInitialSize)
     : buffer_(kCheapPrepend + initialSize),
diff --git a/muduo/net/Connector.h b/muduo/net/Connector.h
index 4b79fb2b2..7b6817d6b 100644
--- a/muduo/net/Connector.h
+++ b/muduo/net/Connector.h
@@ -45,8 +45,8 @@ class Connector : noncopyable,
 
  private:
   enum States { kDisconnected, kConnecting, kConnected };
-  static const int kMaxRetryDelayMs = 30*1000;
-  static const int kInitRetryDelayMs = 500;
+  static constexpr int kMaxRetryDelayMs = 30*1000;
+  static constexpr int kInitRetryDelayMs = 500;
 
   void setState(States s) { state_ = s; }
   void startInLoop();
diff --git a/muduo/net/poller/EPollPoller.h b/muduo/net/poller/EPollPoller.h
index c112f1881..13da94cea 100644
--- a/muduo/net/poller/EPollPoller.h
+++ b/muduo/net/poller/EPollPoller.h
@@ -36,7 +36,7 @@ class EPollPoller : public Poller
   void removeChannel(Channel* channel) override;
 
  private:
-  static const int kInitEventListSize = 16;
+  static constexpr int kInitEventListSize = 16;
 
   static const char* operationToString(int op);