diff --git a/code/Main.c b/code/Main.c
index 9030e33..769abd2 100644
--- a/code/Main.c
+++ b/code/Main.c
@@ -179,6 +179,17 @@ UINT juliana_run()
 
 int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow)
 {
+	CreateMutex(NULL, FALSE, APPLICATION_NAME);
+	if (ERROR_ALREADY_EXISTS == GetLastError()) {
+		MessageBox(
+			NULL,
+			APPLICATION_NAME L" is al gestart.",
+			APPLICATION_NAME,
+			MB_OK | MB_ICONERROR
+		);
+		return 0;
+	}
+
 	juliana_init(hInstance);
 
 	nfc_init();
diff --git a/misc/msvc/JulianaNFC.sln b/misc/msvc/JulianaNFC.sln
index 0ed779d..1020ed5 100644
--- a/misc/msvc/JulianaNFC.sln
+++ b/misc/msvc/JulianaNFC.sln
@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.27004.2006
+VisualStudioVersion = 15.0.27004.2008
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "JulianaNFC", "JulianaNFC.vcxproj", "{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}"
 EndProject
@@ -9,6 +9,8 @@ Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|x64 = Debug|x64
 		Debug|x86 = Debug|x86
+		DefaultBuild|x64 = DefaultBuild|x64
+		DefaultBuild|x86 = DefaultBuild|x86
 		Release|x64 = Release|x64
 		Release|x86 = Release|x86
 	EndGlobalSection
@@ -17,6 +19,10 @@ Global
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Debug|x64.Build.0 = Debug|x64
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Debug|x86.ActiveCfg = Debug|Win32
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Debug|x86.Build.0 = Debug|Win32
+		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.DefaultBuild|x64.ActiveCfg = Debug|x64
+		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.DefaultBuild|x64.Build.0 = Debug|x64
+		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.DefaultBuild|x86.ActiveCfg = Debug|Win32
+		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.DefaultBuild|x86.Build.0 = Debug|Win32
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Release|x64.ActiveCfg = Release|x64
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Release|x64.Build.0 = Release|x64
 		{71B2B17F-9C7B-4834-9751-C4FF5BBF0275}.Release|x86.ActiveCfg = Release|Win32