diff --git a/ThrowBack/TBProphylaxis.h b/ThrowBack/TBProphylaxis.h
new file mode 100644
index 0000000..3825ff8
--- /dev/null
+++ b/ThrowBack/TBProphylaxis.h
@@ -0,0 +1,13 @@
+//
+//  TBProphylaxis.h
+//  WWDC
+//
+//  Created by Guilherme Rambo on 14/05/17.
+//  Copyright © 2017 Guilherme Rambo. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface TBProphylaxis : NSObject
+
+@end
diff --git a/ThrowBack/TBProphylaxis.m b/ThrowBack/TBProphylaxis.m
new file mode 100644
index 0000000..fe829ba
--- /dev/null
+++ b/ThrowBack/TBProphylaxis.m
@@ -0,0 +1,43 @@
+//
+//  TBProphylaxis.m
+//  WWDC
+//
+//  Created by Guilherme Rambo on 14/05/17.
+//  Copyright © 2017 Guilherme Rambo. All rights reserved.
+//
+
+#import "TBProphylaxis.h"
+
+@import Cocoa;
+
+@implementation TBProphylaxis
+
++ (void)load
+{
+    NSArray <NSRunningApplication *> *apps = [NSRunningApplication runningApplicationsWithBundleIdentifier:@"br.com.guilhermerambo.WWDC"];
+    
+    BOOL shouldQuit = NO;
+    
+    for (NSRunningApplication *app in apps) {
+        NSBundle *bundle = [NSBundle bundleWithURL:app.bundleURL];
+        NSString *shortVersion = bundle.infoDictionary[@"CFBundleShortVersionString"];
+        double shortVersionNumber = [shortVersion doubleValue];
+        
+        if (shortVersionNumber < 5) {
+            if (![app forceTerminate]) {
+                shouldQuit = YES;
+            }
+        }
+    }
+    
+    if (shouldQuit) {
+        NSAlert *alert = [NSAlert new];
+        alert.messageText = @"Older version running";
+        alert.informativeText = @"There's an older version of WWDC for macOS running. Version 5 can't work with older versions. Please quit the other version and launch Version 5 again.";
+        [alert addButtonWithTitle:@"OK"];
+        [alert runModal];
+        exit(1);
+    }
+}
+
+@end
diff --git a/WWDC.xcodeproj/project.pbxproj b/WWDC.xcodeproj/project.pbxproj
index 92a8568..ae175c7 100644
--- a/WWDC.xcodeproj/project.pbxproj
+++ b/WWDC.xcodeproj/project.pbxproj
@@ -118,6 +118,8 @@
 		DDB3529C1EC8AB5D00254815 /* WWDCLayer.swift in Sources */ = {isa = PBXBuildFile; fileRef = DDB3529B1EC8AB5D00254815 /* WWDCLayer.swift */; };
 		DDB3529E1EC8D8CD00254815 /* main.m in Sources */ = {isa = PBXBuildFile; fileRef = DDB3529D1EC8D8CD00254815 /* main.m */; };
 		DDB352A01EC9088000254815 /* WWDCTableView.swift in Sources */ = {isa = PBXBuildFile; fileRef = DDB3529F1EC9088000254815 /* WWDCTableView.swift */; };
+		DDB352A51EC90ACA00254815 /* TBProphylaxis.h in Headers */ = {isa = PBXBuildFile; fileRef = DDB352A31EC90ACA00254815 /* TBProphylaxis.h */; };
+		DDB352A61EC90ACA00254815 /* TBProphylaxis.m in Sources */ = {isa = PBXBuildFile; fileRef = DDB352A41EC90ACA00254815 /* TBProphylaxis.m */; };
 		DDCE7ECD1EA7A0F800C7A3CA /* MainWindowController.swift in Sources */ = {isa = PBXBuildFile; fileRef = DDCE7ECC1EA7A0F800C7A3CA /* MainWindowController.swift */; };
 		DDCE7ED21EA7A1D300C7A3CA /* WWDCAppearance.m in Sources */ = {isa = PBXBuildFile; fileRef = DDCE7ED11EA7A1D300C7A3CA /* WWDCAppearance.m */; };
 		DDCE7ED91EA7A86600C7A3CA /* AppCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = DDCE7ED81EA7A86600C7A3CA /* AppCoordinator.swift */; };
@@ -353,6 +355,8 @@
 		DDB3529B1EC8AB5D00254815 /* WWDCLayer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WWDCLayer.swift; sourceTree = "<group>"; };
 		DDB3529D1EC8D8CD00254815 /* main.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = main.m; sourceTree = "<group>"; };
 		DDB3529F1EC9088000254815 /* WWDCTableView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WWDCTableView.swift; sourceTree = "<group>"; };
+		DDB352A31EC90ACA00254815 /* TBProphylaxis.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = TBProphylaxis.h; sourceTree = "<group>"; };
+		DDB352A41EC90ACA00254815 /* TBProphylaxis.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = TBProphylaxis.m; sourceTree = "<group>"; };
 		DDBFA16A1EB525F2004AE10F /* PlayerUI.xcodeproj */ = {isa = PBXFileReference; lastKnownFileType = "wrapper.pb-project"; name = PlayerUI.xcodeproj; path = PlayerUI/PlayerUI.xcodeproj; sourceTree = "<group>"; };
 		DDCE7ECC1EA7A0F800C7A3CA /* MainWindowController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MainWindowController.swift; sourceTree = "<group>"; };
 		DDCE7ECF1EA7A1D300C7A3CA /* WWDC-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "WWDC-Bridging-Header.h"; sourceTree = "<group>"; };
@@ -853,6 +857,8 @@
 			children = (
 				DDDAA3F11EC7653300DF9D02 /* Info.plist */,
 				DDDAA3F01EC7653300DF9D02 /* ThrowBack.h */,
+				DDB352A31EC90ACA00254815 /* TBProphylaxis.h */,
+				DDB352A41EC90ACA00254815 /* TBProphylaxis.m */,
 				DDDAA4001EC768A900DF9D02 /* Migration */,
 			);
 			path = ThrowBack;
@@ -936,6 +942,7 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				DDB352A51EC90ACA00254815 /* TBProphylaxis.h in Headers */,
 				DDDAA3F21EC7653300DF9D02 /* ThrowBack.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -1285,6 +1292,7 @@
 				DDDAA4071EC76D9300DF9D02 /* TBPreferences.swift in Sources */,
 				DDDAA40A1EC775B500DF9D02 /* TBSession.swift in Sources */,
 				DDDAA4021EC768C500DF9D02 /* TBUserDataMigrator.swift in Sources */,
+				DDB352A61EC90ACA00254815 /* TBProphylaxis.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};