diff --git a/deploy/windows/installer/build-installer.ps1 b/deploy/windows/installer/build-installer.ps1
index bba59a2..3930c30 100644
--- a/deploy/windows/installer/build-installer.ps1
+++ b/deploy/windows/installer/build-installer.ps1
@@ -260,7 +260,7 @@ it must not be shipped.
 '@
     }
 } else {
-    $problems = Test-BundleLock -BundleRoot $BundleRoot -Lock $lock
+    $problems = @(Test-BundleLock -BundleRoot $BundleRoot -Lock $lock)
     if ($problems.Count -eq 0) {
         Say ("    payload matches the lock ({0}, {1})" -f `
              (Get-JsonProperty $lock 'pythontag' 'unknown'), (Get-JsonProperty $lock 'platform' 'unknown')) 'Green'
diff --git a/deploy/windows/installer/bundle-lock.ps1 b/deploy/windows/installer/bundle-lock.ps1
index 6fc2843..1acfde8 100644
--- a/deploy/windows/installer/bundle-lock.ps1
+++ b/deploy/windows/installer/bundle-lock.ps1
@@ -206,7 +206,11 @@ function Test-BundleLock {
         }
     }
     $problems += Test-WheelhouseCoversRequirements -BundleRoot $BundleRoot
-    return $problems
+    # The comma keeps this an ARRAY through the return. Without it PowerShell
+    # unrolls an empty result to $null and a single result to a bare string, and
+    # every caller that asks for .Count then behaves differently depending on how
+    # many problems there happen to be.
+    return ,$problems
 }
 
 function Test-WheelhouseCoversRequirements {
diff --git a/deploy/windows/installer/shopdb-install.ps1 b/deploy/windows/installer/shopdb-install.ps1
index 678fecf..2347d4d 100644
--- a/deploy/windows/installer/shopdb-install.ps1
+++ b/deploy/windows/installer/shopdb-install.ps1
@@ -309,7 +309,12 @@ function Assert-BundleIntegrity {
     }
     . $checker
     $lock = Read-BundleLock $lockFile
-    $problems = Test-BundleLock -BundleRoot $BundleRoot -Lock $lock
+    # @() around the call, NOT just the assignment. PowerShell unrolls a
+    # zero-element return into $null, and under Set-StrictMode 2.0 $null.Count
+    # THROWS - so a bundle that verified perfectly cleanly crashed stage 2 with
+    # "The property 'Count' cannot be found on this object". The success path was
+    # the broken one, which is why it survived every failing test.
+    $problems = @(Test-BundleLock -BundleRoot $BundleRoot -Lock $lock)
     if ($problems.Count -gt 0) {
         foreach ($p in $problems) { Write-Log "  $p" 'FAIL' }
         Fail ("the bundle does not match bundle-lock.json ({0} problem(s))" -f $problems.Count) @'