diff --git a/Greenshot/releases/additional_files/readme.txt b/Greenshot/releases/additional_files/readme.txt
index bf5ae591e..2b996d9b7 100644
--- a/Greenshot/releases/additional_files/readme.txt
+++ b/Greenshot/releases/additional_files/readme.txt
@@ -3,7 +3,7 @@ Greenshot: A screenshot tool optimized for productivity. Save a screenshot or a
 
 CHANGE LOG:
 
-1.0.0 build 1852
+1.0.0 build 1858 (Unstable, meaning we are in testing fase and haven't released yet)
 
 We changed the version to 1.0.0, after 5 year the version should no longer have a "beta" feeling!
 
diff --git a/Greenshot/releases/innosetup/setup.iss b/Greenshot/releases/innosetup/setup.iss
index 0a7ab05fa..353f6b29c 100644
--- a/Greenshot/releases/innosetup/setup.iss
+++ b/Greenshot/releases/innosetup/setup.iss
@@ -211,6 +211,72 @@ Name: "languages\zhCN"; Description: "简体中文"; Types: Full; Check: hasLang
 Name: "languages\zhTW"; Description: "繁體中文"; Types: Full; Check: hasLanguageGroup('9')
 [Code]
 
+/////////////////////////////////////////////////////////////////////
+// The following uninstall code was found at:
+// http://stackoverflow.com/questions/2000296/innosetup-how-to-automatically-uninstall-previous-installed-version
+/////////////////////////////////////////////////////////////////////
+function GetUninstallString(): String;
+var
+	sUnInstPath: String;
+	sUnInstallString: String;
+begin
+	sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{#emit SetupSetting("AppId")}_is1');
+	sUnInstallString := '';
+	// Retrieve uninstall string from HKLM or HKCU
+	if not RegQueryStringValue(HKLM, sUnInstPath, 'UninstallString', sUnInstallString) then
+		RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
+	Result := sUnInstallString;
+end;
+
+
+/////////////////////////////////////////////////////////////////////
+function IsUpgrade(): Boolean;
+begin
+	Result := (GetUninstallString() <> '');
+end;
+
+/////////////////////////////////////////////////////////////////////
+function UnInstallOldVersion(): Integer;
+var
+	sUnInstallString: String;
+	iResultCode: Integer;
+begin
+// Return Values:
+// 1 - uninstall string is empty
+// 2 - error executing the UnInstallString
+// 3 - successfully executed the UnInstallString
+
+	// default return value
+	Result := 0;
+
+	// get the uninstall string of the old app
+	sUnInstallString := GetUninstallString();
+	if sUnInstallString <> '' then
+	begin
+		sUnInstallString := RemoveQuotes(sUnInstallString);
+		if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
+			Result := 3
+		else
+			Result := 2;
+	end else
+		Result := 1;
+end;
+
+/////////////////////////////////////////////////////////////////////
+procedure CurStepChanged(CurStep: TSetupStep);
+begin
+	if (CurStep=ssInstall) then
+	begin
+		if (IsUpgrade()) then
+		begin
+			UnInstallOldVersion();
+		end;
+	end;
+end;
+/////////////////////////////////////////////////////////////////////
+// End of unstall code
+/////////////////////////////////////////////////////////////////////
+
 // Build a list of greenshot parameters from the supplied installer parameters
 function GetParamsForGS(argument: String): String;
 var