diff --git a/WinUtil.cpp b/WinUtil.cpp
index 5cdf9ed..141dcdd 100644
--- a/WinUtil.cpp
+++ b/WinUtil.cpp
@@ -72,14 +72,29 @@ DWORD NamedMutex::getError() const
     return errcode;
 }
 
-void NamedMutex::wait()
+int NamedMutex::wait()
 {
-    WaitForSingleObject(hmtx,INFINITE);
+    return wait_for(INFINITE);
 }
 
-void NamedMutex::wait_for(int ms)
+int NamedMutex::wait_for(int ms)
 {
-    WaitForSingleObject(hmtx,ms);
+    DWORD ret=WaitForSingleObject(hmtx,ms);
+    if(ret==WAIT_OBJECT_0)
+    {
+        return 1;
+    }
+    else if(ret==WAIT_TIMEOUT)
+    {
+        return 0;
+    }
+    else
+    {
+        // WAIT_ABANDONED
+        // WAIT_FAILED
+        errcode=GetLastError();
+        return -1;
+    }
 }
 
 void NamedMutex::release()
diff --git a/WinUtil.h b/WinUtil.h
index 60c5949..cbd608b 100644
--- a/WinUtil.h
+++ b/WinUtil.h
@@ -29,8 +29,8 @@ public:
     DWORD getError() const;
 
     /// If the mutex has been occupied by this process, wait() will return immediately.
-    void wait();
-    void wait_for(int ms);
+    int wait();
+    int wait_for(int ms);
     void release();
 private:
     HANDLE hmtx;