diff --git a/deploy/FortFirewall.iss b/deploy/FortFirewall.iss
index 463042be..852d512e 100644
--- a/deploy/FortFirewall.iss
+++ b/deploy/FortFirewall.iss
@@ -9,6 +9,7 @@
 ; NOTE: The value of AppId uniquely identifies this application.
 ; Do not use the same AppId value in installers for other applications.
 ; (To generate a new GUID, click Tools | Generate GUID inside the IDE.)
+AppMutex={#APP_NAME}
 AppName={#APP_NAME}
 AppVersion={#APP_VERSION_STR}
 AppVerName={#APP_NAME}
diff --git a/src/ui/fortcommon.cpp b/src/ui/fortcommon.cpp
index 1015e5ac..bf638e66 100644
--- a/src/ui/fortcommon.cpp
+++ b/src/ui/fortcommon.cpp
@@ -1,7 +1,6 @@
 #include "fortcommon.h"
 
-#define _WIN32_WINNT	0x0600
-
+#define _WIN32_WINNT    0x0600
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 #include <winioctl.h>
diff --git a/src/ui/main.cpp b/src/ui/main.cpp
index 1ab06477..e7bc815c 100644
--- a/src/ui/main.cpp
+++ b/src/ui/main.cpp
@@ -5,9 +5,12 @@
 #include "fortcommon.h"
 #include "fortmanager.h"
 #include "fortsettings.h"
+#include "util/osutil.h"
 
 int main(int argc, char *argv[])
 {
+    OsUtil::createGlobalMutex(APP_NAME);
+
     QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 
     QApplication app(argc, argv);
diff --git a/src/ui/util/osutil.cpp b/src/ui/util/osutil.cpp
index b05d7b45..b731e040 100644
--- a/src/ui/util/osutil.cpp
+++ b/src/ui/util/osutil.cpp
@@ -5,6 +5,9 @@
 #include <QPixmap>
 #include <QImage>
 
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
 #include "processinfo.h"
 
 OsUtil::OsUtil(QObject *parent) :
@@ -33,3 +36,8 @@ QString OsUtil::pidToDosPath(quint32 pid)
     const ProcessInfo pi(pid);
     return pi.dosPath();
 }
+
+bool OsUtil::createGlobalMutex(const char *name)
+{
+    return !CreateMutexA(NULL, FALSE, name);
+}
diff --git a/src/ui/util/osutil.h b/src/ui/util/osutil.h
index 78e28990..2b344cbc 100644
--- a/src/ui/util/osutil.h
+++ b/src/ui/util/osutil.h
@@ -14,6 +14,8 @@ public:
     Q_INVOKABLE static void setClipboardData(const QVariant &data);
 
     Q_INVOKABLE static QString pidToDosPath(quint32 pid);
+
+    static bool createGlobalMutex(const char *name);
 };
 
 #endif // OSUTIL_H