diff --git a/.build.ps1 b/.build.ps1
index 607e467..bb53777 100644
--- a/.build.ps1
+++ b/.build.ps1
@@ -86,7 +86,7 @@ task module version, markdown, help, {
 	CompanyName = 'Roman Kuzmin'
 	Copyright = '(c) Roman Kuzmin'
 	Description = 'Build and test automation in PowerShell'
-	PowerShellVersion = '2.0'
+	PowerShellVersion = '3.0'
 	AliasesToExport = 'Invoke-Build', 'Build-Checkpoint', 'Build-Parallel'
 	PrivateData = @{
 		PSData = @{
@@ -114,7 +114,7 @@ task nuget module, {
 	# summary and description
 	$text = @'
 Invoke-Build is a build and test automation tool which invokes tasks defined in
-PowerShell v2.0+ scripts. It is similar to psake but arguably easier to use and
+PowerShell v3.0+ scripts. It is similar to psake but arguably easier to use and
 more powerful. It is complete, bug free, well covered by tests.
 '@
 
diff --git a/.github/workflows/test2.yml b/.github/workflows/test2.yml
deleted file mode 100644
index 68706aa..0000000
--- a/.github/workflows/test2.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-name: test2
-
-on:
-  workflow_dispatch:
-  push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
-
-jobs:
-  test2:
-    runs-on: windows-latest
-    steps:
-      - uses: actions/checkout@v4
-      - name: boot
-        shell: powershell
-        run: ./Invoke-Build.ps1 boot
-      - name: test
-        shell: cmd
-        run: powershell -Version 2 ./Invoke-Build.ps1 . Tests/.build.ps1
diff --git a/Invoke-Build.ps1 b/Invoke-Build.ps1
index d06b377..684c7a8 100644
--- a/Invoke-Build.ps1
+++ b/Invoke-Build.ps1
@@ -235,9 +235,12 @@ function Get-BuildSynopsis([Parameter(Mandatory=1)]$Task, $Hash=${*}.H) {
 function Use-BuildEnv([Parameter(Mandatory=1)][hashtable]$Env, [Parameter(Mandatory=1)][scriptblock]$Script) {
 	${private:*e} = @{}
 	${private:*s} = $Script
+	function *set($n, $v) {
+		[Environment]::SetEnvironmentVariable($n, $(if ($null -eq $v) {[System.Management.Automation.Language.NullString]::Value} else {$v}))
+	}
 	foreach($_ in $Env.GetEnumerator()) {
 		${*e}[$_.Key] = [Environment]::GetEnvironmentVariable($_.Key)
-		[Environment]::SetEnvironmentVariable($_.Key, $_.Value)
+		*set $_.Key $_.Value
 	}
 	Remove-Variable Env, Script
 	try {
@@ -245,7 +248,7 @@ function Use-BuildEnv([Parameter(Mandatory=1)][hashtable]$Env, [Parameter(Mandat
 	}
 	finally {
 		foreach($_ in ${*e}.GetEnumerator()) {
-			[Environment]::SetEnvironmentVariable($_.Key, $_.Value)
+			*set $_.Key $_.Value
 		}
 	}
 }
diff --git a/README.md b/README.md
index 49ac3b4..35b5570 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@
 ## Build Automation in PowerShell
 
 Invoke-Build is a build and test automation tool which invokes tasks defined in
-PowerShell v2.0+ scripts. It is similar to psake but arguably easier to use and
+PowerShell v3.0+ scripts. It is similar to psake but arguably easier to use and
 more powerful. It is complete, bug free, well covered by tests.
 
 In addition to basic task processing the engine supports
diff --git a/Release-Notes.md b/Release-Notes.md
index c9df451..7d22dd1 100644
--- a/Release-Notes.md
+++ b/Release-Notes.md
@@ -1,6 +1,14 @@
 # Invoke-Build Release Notes
 
-`Show-BuildGraph.ps1` - use viz-3.9.0
+## v5.12.0
+
+Stop supporting and testing PowerShell v2.0 (unlikely practical).
+
+Fix `Use-BuildEnv` potential issues in PowerShell 7.5.
+
+Fix `ib` dotnet tool similar potential issues.
+
+`Show-BuildGraph.ps1` - use viz-3.11.0
 
 ## v5.11.3
 
diff --git a/Show-BuildGraph.ps1 b/Show-BuildGraph.ps1
index e9b04f8..d9439ea 100644
--- a/Show-BuildGraph.ps1
+++ b/Show-BuildGraph.ps1
@@ -1,5 +1,5 @@
 <#PSScriptInfo
-.VERSION 1.0.8
+.VERSION 1.0.9
 .AUTHOR Roman Kuzmin
 .COPYRIGHT (c) Roman Kuzmin
 .TAGS Invoke-Build, Graphviz
@@ -102,7 +102,7 @@ else {
 		$jsUrl = 'file:///' + $app.Source.Replace('\', '/')
 	}
 	else {
-		$jsUrl = 'https://github.com/mdaines/viz-js/releases/download/release-viz-3.9.0/viz-standalone.js'
+		$jsUrl = 'https://github.com/mdaines/viz-js/releases/download/release-viz-3.11.0/viz-standalone.js'
 	}
 }
 
diff --git a/Tests/.build.ps1 b/Tests/.build.ps1
index fed3096..cf6c443 100644
--- a/Tests/.build.ps1
+++ b/Tests/.build.ps1
@@ -196,9 +196,7 @@ task TestSelfAlias {
 }
 
 # Synopsis: Test a build invoked from a background job just to be sure it works.
-task TestStartJob -If {
-	!($PSVersionTable.PSVersion.Major -eq 2 -and $env:GITHUB_ACTION) -and !($Host.Name -eq 'FarHost')
-} {
+task TestStartJob -If {$Host.Name -ne 'FarHost'} {
 	$job = Start-Job { Invoke-Build . $args[0] } -ArgumentList "$BuildRoot\Dynamic.build.ps1"
 	$log = Wait-Job $job | Receive-Job
 	Remove-Job $job
diff --git a/Tests/Build-Parallel/Parallel.test.ps1 b/Tests/Build-Parallel/Parallel.test.ps1
index 8b1dca3..9566b49 100644
--- a/Tests/Build-Parallel/Parallel.test.ps1
+++ b/Tests/Build-Parallel/Parallel.test.ps1
@@ -209,7 +209,7 @@ task OmittedBuildParameterFile {
 # Covers #27, [IB] was not found before loading IB.
 task ParallelEmptyRun {
 	($r = Invoke-PowerShell -NoProfile -Command 'Build-Parallel.ps1 -Result r; $r.GetType().Name')
-	equals $r $(if ($PSVersionTable.PSVersion.Major -eq 2) {'Hashtable'} else {'PSCustomObject'})
+	equals $r PSCustomObject
 }
 
 # Covers #93 with the new switch FailHard.
diff --git a/Tests/Convert-psake/Convert-psake.test.ps1 b/Tests/Convert-psake/Convert-psake.test.ps1
index f8db808..34dec21 100644
--- a/Tests/Convert-psake/Convert-psake.test.ps1
+++ b/Tests/Convert-psake/Convert-psake.test.ps1
@@ -4,6 +4,6 @@
 #>
 
 # Synopsis: Invoke Convert-psake.ps1. Output is to be compared.
-task Convert-psake -If ($PSVersionTable.PSVersion.Major -ge 3) {
+task Convert-psake {
 	Convert-psake default.ps1 -Invoke -Synopsis
 }
diff --git a/Tests/CountKeysValues/.test.ps1 b/Tests/CountKeysValues/.test.ps1
index 3bb16b3..218505c 100644
--- a/Tests/CountKeysValues/.test.ps1
+++ b/Tests/CountKeysValues/.test.ps1
@@ -30,7 +30,7 @@ task Show-BuildTree {
 }
 
 # used to out funny parameters and environment
-task WhatIf -If ($PSVersionTable.PSVersion.Major -ne 2) {
+task WhatIf {
 	($r = Invoke-Build -WhatIf | Out-String)
 	$r = Remove-Ansi ($r -replace ' ' -replace '\r?\n', '|')
 	assert ($r.Contains('|Parameters:|[Object]Count|[Object]Keys|[Object]Values|Environment:|Count,Keys,Values|'))
@@ -78,7 +78,7 @@ task Show-BuildGraph -If (!(Test-Unix) -and !$env:GITHUB_ACTION) {
 }
 
 # used to generate just `values`
-task New-VSCodeTask -If ($PSVersionTable.PSVersion.Major -ne 2) {
+task New-VSCodeTask {
 	New-VSCodeTask.ps1
 	$r = (Get-Content .vscode/tasks.json | Out-String) -replace '\s+', ' '
 	assert ($r.Contains('"label": "count"'))
diff --git a/Tests/Exec.test.ps1 b/Tests/Exec.test.ps1
index 3f3523b..ab6bd35 100644
--- a/Tests/Exec.test.ps1
+++ b/Tests/Exec.test.ps1
@@ -5,8 +5,6 @@
 
 Import-Module .\Tools
 
-$PSv3 = $PSVersionTable.PSVersion.Major -ge 3
-
 task ExecWorksCode0 {
 	$r = exec {
 		if (Test-Unix) {
@@ -83,7 +81,7 @@ task ExecShouldUseGlobalLastExitCode {
 }
 
 # New switch Echo, #176 #179
-task Echo1 -If $PSv3 {
+task Echo1 {
 	# different kind variables
 	$env:SOME_VAR = 'SOME_VAR'
 	$script:foo = 'foo'
@@ -142,7 +140,7 @@ task ErrorMessage {
 }
 
 # #192
-task Echo2 -If $PSv3 {
+task Echo2 {
 	function *Write { $args[1] }
 
 	#! 1 line, make 1 leading and trailing space
@@ -215,7 +213,7 @@ task StdErrBadCommand {
 }
 
 # Echo properties, #221
-task EchoProperties -If $PSv3 {
+task EchoProperties {
 	Set-Alias Write-Build Write-Build-Fake
 	function Write-Build-Fake($Color, $Text) {$Text}
 
diff --git a/Tests/Issues/217-bad-error-on-unknown-parameter/217.test.ps1 b/Tests/Issues/217-bad-error-on-unknown-parameter/217.test.ps1
index d6ea9b3..9e886c8 100644
--- a/Tests/Issues/217-bad-error-on-unknown-parameter/217.test.ps1
+++ b/Tests/Issues/217-bad-error-on-unknown-parameter/217.test.ps1
@@ -16,17 +16,11 @@ task UnknownParameter {
 
 	# parameter positions after IB
 	$b1, $b2, $b3 = Get-ParameterPosition
-	if ($PSVersionTable.PSVersion.Major -eq 2) {
-		equals $b1 $a1
-		equals $b2 $a2
-		equals $b3 $a3
-	}
-	else {
-		# shifted +2 on every call
-		equals $b1 ($a1 + 2)
-		equals $b2 ($a2 + 2)
-		equals $b3 ($a3 + 2)
-	}
+
+	# shifted +2 on every call
+	equals $b1 ($a1 + 2)
+	equals $b2 ($a2 + 2)
+	equals $b3 ($a3 + 2)
 }
 
 function Get-ParameterPosition {
diff --git a/Tests/New-VSCodeTask/.test.ps1 b/Tests/New-VSCodeTask/.test.ps1
index 3d40ef8..dd6dd2a 100644
--- a/Tests/New-VSCodeTask/.test.ps1
+++ b/Tests/New-VSCodeTask/.test.ps1
@@ -3,8 +3,6 @@
 	Tests New-VSCodeTask.ps1
 #>
 
-if ($PSVersionTable.PSVersion.Major -eq 2) {return task skipV2}
-
 Import-Module ..\Tools
 Set-StrictMode -Off
 
diff --git a/Tests/TaskHelp.test.ps1 b/Tests/TaskHelp.test.ps1
index 37ccb7d..2b4bcf9 100644
--- a/Tests/TaskHelp.test.ps1
+++ b/Tests/TaskHelp.test.ps1
@@ -66,7 +66,7 @@ task Test {
 
 # Use this repo build script, test code and tree processing.
 # 2024-02-29 v2 started to fail, skip.
-task UndocumentedStuff -If ($PSVersionTable.PSVersion.Major -ge 3) {
+task UndocumentedStuff {
 	# call by WhatIf
 	Invoke-Build -File ../.build.ps1 -WhatIf
 
@@ -190,12 +190,10 @@ task IfInputsOutputs {
 
 	# call and test
 	$r = Show-TaskHelp t1 z.ps1 -Format {$args[0]}
-	if ($PSVersionTable.PSVersion.Major -ge 3) {
-		equals $r.Parameters.Count 3
-		equals $r.Parameters[0].Name If
-		equals $r.Parameters[1].Name Inputs
-		equals $r.Parameters[2].Name Outputs
-	}
+	equals $r.Parameters.Count 3
+	equals $r.Parameters[0].Name If
+	equals $r.Parameters[1].Name Inputs
+	equals $r.Parameters[2].Name Outputs
 
 	Remove-Item z.ps1
 }
diff --git a/ib/Program.cs b/ib/Program.cs
index 80e8e63..a45176e 100644
--- a/ib/Program.cs
+++ b/ib/Program.cs
@@ -75,8 +75,9 @@ If the environment variable `pwsh` is defined it is used as pwsh.
                 return 0;
             }
 
-            var app = Environment.GetEnvironmentVariable("pwsh")
-                ?? (options.UsePwsh || Environment.OSVersion.Platform != PlatformID.Win32NT ? "pwsh" : "powershell");
+            var app = Environment.GetEnvironmentVariable("pwsh");
+            if (string.IsNullOrEmpty(app))
+                app = options.UsePwsh || Environment.OSVersion.Platform != PlatformID.Win32NT ? "pwsh" : "powershell";
 
             var root = Path.GetDirectoryName(typeof(Program).Assembly.Location);
             var ib = Path.Combine(root, "../../../InvokeBuild/Invoke-Build.ps1");