diff --git a/ArchiSteamFarm/ArchiSteamFarm.csproj b/ArchiSteamFarm/ArchiSteamFarm.csproj
index 1c5801500..c8c077220 100644
--- a/ArchiSteamFarm/ArchiSteamFarm.csproj
+++ b/ArchiSteamFarm/ArchiSteamFarm.csproj
@@ -138,6 +138,7 @@
     <Compile Include="Logging.cs" />
     <Compile Include="InMemoryServerListProvider.cs" />
     <Compile Include="MobileAuthenticator.cs" />
+    <Compile Include="OS.cs" />
     <Compile Include="Runtime.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
diff --git a/ArchiSteamFarm/OS.cs b/ArchiSteamFarm/OS.cs
new file mode 100644
index 000000000..9125810b5
--- /dev/null
+++ b/ArchiSteamFarm/OS.cs
@@ -0,0 +1,69 @@
+/*
+    _                _      _  ____   _                           _____
+   / \    _ __  ___ | |__  (_)/ ___| | |_  ___   __ _  _ __ ___  |  ___|__ _  _ __  _ __ ___
+  / _ \  | '__|/ __|| '_ \ | |\___ \ | __|/ _ \ / _` || '_ ` _ \ | |_  / _` || '__|| '_ ` _ \
+ / ___ \ | |  | (__ | | | || | ___) || |_|  __/| (_| || | | | | ||  _|| (_| || |   | | | | | |
+/_/   \_\|_|   \___||_| |_||_||____/  \__|\___| \__,_||_| |_| |_||_|   \__,_||_|   |_| |_| |_|
+
+ Copyright 2015-2017 Łukasz "JustArchi" Domeradzki
+ Contact: JustArchi@JustArchi.net
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+					
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+*/
+
+using System;
+using System.Runtime.InteropServices;
+using ArchiSteamFarm.Localization;
+
+namespace ArchiSteamFarm {
+	internal static class OS {
+		private static readonly PlatformID PlatformID = Environment.OSVersion.Platform;
+
+		internal static void Init() {
+			switch (PlatformID) {
+				case PlatformID.Win32NT:
+				case PlatformID.Win32S:
+				case PlatformID.Win32Windows:
+				case PlatformID.WinCE:
+					KeepWindowsSystemActive();
+					break;
+			}
+		}
+
+		private static void KeepWindowsSystemActive() {
+			// This function calls unmanaged API in order to tell Windows OS that it should not enter sleep state while the program is running
+			// If user wishes to enter sleep mode, then he should use ShutdownOnFarmingFinished or manage ASF process with third-party tool or script
+			// More info: https://msdn.microsoft.com/library/windows/desktop/aa373208(v=vs.85).aspx
+			EExecutionState result = SetThreadExecutionState(EExecutionState.Continuous | EExecutionState.AwayModeRequired | EExecutionState.SystemRequired);
+
+			// SetThreadExecutionState() returns NULL on failure, which is mapped to 0 (EExecutionState.Error) in our case
+			if (result == EExecutionState.Error) {
+				ASF.ArchiLogger.LogGenericError(string.Format(Strings.WarningFailedWithError, result));
+			}
+		}
+
+		[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
+		private static extern EExecutionState SetThreadExecutionState(EExecutionState executionState);
+
+		[Flags]
+		private enum EExecutionState : uint {
+			Error = 0,
+			SystemRequired = 0x00000001,
+//			DisplayRequired = 0x00000002,
+//			UserPresent = 0x00000004,
+			AwayModeRequired = 0x00000040,
+			Continuous = 0x80000000
+		}
+	}
+}
\ No newline at end of file
diff --git a/ArchiSteamFarm/Program.cs b/ArchiSteamFarm/Program.cs
index 4c810cacb..4e1a7a186 100644
--- a/ArchiSteamFarm/Program.cs
+++ b/ArchiSteamFarm/Program.cs
@@ -266,8 +266,9 @@ namespace ArchiSteamFarm {
 			}
 
 			ArchiWebHandler.Init();
-			WebBrowser.Init();
+			OS.Init();
 			WCF.Init();
+			WebBrowser.Init();
 
 			WebBrowser = new WebBrowser(ASF.ArchiLogger);
 		}
diff --git a/GUI/GUI.csproj b/GUI/GUI.csproj
index e01b8c7c8..2fe895c74 100644
--- a/GUI/GUI.csproj
+++ b/GUI/GUI.csproj
@@ -148,6 +148,9 @@
     <Compile Include="..\ArchiSteamFarm\MobileAuthenticator.cs">
       <Link>MobileAuthenticator.cs</Link>
     </Compile>
+    <Compile Include="..\ArchiSteamFarm\OS.cs">
+      <Link>OS.cs</Link>
+    </Compile>
     <Compile Include="..\ArchiSteamFarm\Runtime.cs">
       <Link>Runtime.cs</Link>
     </Compile>