diff --git a/.gitignore b/.gitignore
index 72e84c0e..da3b0bf9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,6 +22,7 @@ dist/
 #  before PyInstaller builds the exe, so as to inject date/other infos into it.
 *.manifest
 *.spec
+.upx/
 
 # Dev settings
 settings.toml
diff --git a/scripts/build.ps1 b/scripts/build.ps1
index 9660b24e..e9d4be48 100644
--- a/scripts/build.ps1
+++ b/scripts/build.ps1
@@ -2,19 +2,21 @@
 
 & "$PSScriptRoot/compile_resources.ps1"
 
+$ProjectRoot = "$PSScriptRoot/.."
 $SupportsSplashScreen = [System.Convert]::ToBoolean($(uv run --active python -c "import _tkinter; print(hasattr(_tkinter, '__file__'))"))
 
 $arguments = @(
-  "$PSScriptRoot/../src/AutoSplit.py",
+  "$ProjectRoot/src/AutoSplit.py",
   '--onefile',
   '--windowed',
-  '--additional-hooks-dir=Pyinstaller/hooks',
   '--optimize 2', # Remove asserts and docstrings for smaller build
-  "--add-data=pyproject.toml$([System.IO.Path]::PathSeparator).",
-  '--icon=res/icon.ico')
+  "--additional-hooks-dir=$ProjectRoot/Pyinstaller/hooks",
+  "--add-data=$ProjectRoot/pyproject.toml$([System.IO.Path]::PathSeparator).",
+  "--upx-dir=$PSScriptRoot/.upx"
+  "--icon=$ProjectRoot/res/icon.ico")
 if ($SupportsSplashScreen) {
   # https://github.com/pyinstaller/pyinstaller/issues/9022
-  $arguments += @('--splash=res/splash.png')
+  $arguments += @("--splash=$ProjectRoot/res/splash.png")
 }
 if ($IsWindows) {
   $arguments += @(
@@ -25,10 +27,10 @@ if ($IsWindows) {
 Start-Process -Wait -NoNewWindow uv -ArgumentList $(@('run', '--active', 'pyinstaller') + $arguments)
 
 If ($IsLinux) {
-  Move-Item -Force $PSScriptRoot/../dist/AutoSplit $PSScriptRoot/../dist/AutoSplit.elf
+  Move-Item -Force $ProjectRoot/dist/AutoSplit $ProjectRoot/dist/AutoSplit.elf
   If ($?) {
     Write-Host 'Added .elf extension'
   }
-  chmod +x $PSScriptRoot/../dist/AutoSplit.elf
+  chmod +x $ProjectRoot/dist/AutoSplit.elf
   Write-Host 'Added execute permission'
 }
diff --git a/scripts/install.ps1 b/scripts/install.ps1
index 941ddeac..e9430ad4 100644
--- a/scripts/install.ps1
+++ b/scripts/install.ps1
@@ -29,7 +29,7 @@ If ($IsLinux) {
   }
 }
 
-# Installing Python dependencies
+# Installing system dependencies
 If ($IsLinux) {
   If (-not $Env:GITHUB_JOB -or $Env:GITHUB_JOB -eq 'Build') {
     sudo apt-get update
@@ -38,8 +38,23 @@ If ($IsLinux) {
   }
 }
 
+# UPX is only used by PyInstaller on Windows
+If ($IsWindows -and [System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture -eq 'X64') {
+  $UPXVersion = '5.0.1'
+  $UPXFolderName = "upx-$UPXVersion-win64"
+  Write-Output "Installing $UPXFolderName"
+  if (Test-Path "$PSScriptRoot/.upx") { Remove-Item $PSScriptRoot/.upx -Recurse }
+  Invoke-WebRequest `
+    -Uri https://github.com/upx/upx/releases/download/v$UPXVersion/$UPXFolderName.zip `
+    -OutFile $Env:TEMP/$UPXFolderName.zip
+  # Automatically install in a local untracked folder. This makes it easy to version and replicate on CI
+  Expand-Archive $Env:TEMP/$UPXFolderName.zip $PSScriptRoot/.upx
+  Move-Item $PSScriptRoot/.upx/$UPXFolderName/* $PSScriptRoot/.upx
+  Remove-Item $PSScriptRoot/.upx/$UPXFolderName
+}
+
 $prod = If ($Env:GITHUB_JOB -eq 'Build') { '--no-dev' } Else { }
-$lock = If ($Env:GITHUB_JOB) { '--locked' } Else { '--upgrade' }
+$lock = If ($Env:GITHUB_JOB) { '--locked' } Else { }
 Write-Output "Installing Python dependencies with: uv sync $prod $lock"
 uv sync --active $prod $lock