--- NotepadNext-git.old/src/singleapplication/singleapplication.cpp
+++ NotepadNext-git/src/singleapplication/singleapplication.cpp
@@ -24,6 +24,7 @@
 #include <QtCore/QElapsedTimer>
 #include <QtCore/QByteArray>
 #include <QtCore/QSharedMemory>
+#include <csignal>
 
 #include "singleapplication.h"
 #include "singleapplication_p.h"
@@ -137,6 +138,10 @@
       }
     }
 
+    if (inst->primary && kill (inst->primaryPid, 0)) {
+        inst->primary = false;
+    }
+
     if( inst->primary == false ){
         d->startPrimary();
         if( ! d->memory->unlock() ){