diff --git a/install.ps1 b/install.ps1
index 5824ad7..19f13cc 100644
--- a/install.ps1
+++ b/install.ps1
@@ -25,10 +25,11 @@ function Require-Command($Name) {
 }
 
 function Normalize-Arch {
-    switch ($env:PROCESSOR_ARCHITECTURE) {
+    $arch = if ($env:PROCESSOR_ARCHITEW6432) { $env:PROCESSOR_ARCHITEW6432 } else { $env:PROCESSOR_ARCHITECTURE }
+    switch ($arch) {
         "AMD64" { "x86_64"; break }
         "ARM64" { "aarch64"; break }
-        default { $env:PROCESSOR_ARCHITECTURE.ToLowerInvariant() }
+        default { if ($arch) { $arch.ToLowerInvariant() } else { "unknown" } }
     }
 }
 
diff --git a/tests/release_scripts.rs b/tests/release_scripts.rs
index 8a24171..1988a3e 100644
--- a/tests/release_scripts.rs
+++ b/tests/release_scripts.rs
@@ -159,6 +159,15 @@ fn windows_installer_adds_user_path_idempotently() {
     assert!(ps1.contains("Add-UserPath $bindir"));
 }
 
+#[test]
+fn windows_installer_prefers_native_wow64_arch_for_prebuilts() {
+    let ps1 = include_str!("../install.ps1");
+    assert!(ps1.contains("PROCESSOR_ARCHITEW6432"));
+    assert!(ps1.contains("$arch = if ($env:PROCESSOR_ARCHITEW6432)"));
+    assert!(ps1.contains("\"ARM64\" { \"aarch64\"; break }"));
+    assert!(ps1.contains("\"dosh-windows-$(Normalize-Arch).zip\""));
+}
+
 #[test]
 fn unix_installer_rejects_unsafe_source_update_cache_paths() {
     let install = include_str!("../install.sh");