diff --git a/scripts/dev/bless_tests.php b/scripts/dev/bless_tests.php
index b38935503ae3..b7388db09175 100755
--- a/scripts/dev/bless_tests.php
+++ b/scripts/dev/bless_tests.php
@@ -5,6 +5,20 @@
     die("Usage: php bless_tests.php dir/\n");
 }
 
+// Build a list of known errors on this platform, so we can avoid hardcoding
+// platform-specific errors in expect output, as the errno/strerror differs
+// between platforms.
+$strerrors = [];
+if (function_exists("posix_strerror")) {
+	for ($i = -1; $i < 255; $i++) {
+		$str = posix_strerror($i);
+		if (str_contains($str, "Unknown error") && $i > 0) {
+			break;
+		}
+		$strerrors[] = $str;
+	}
+}
+
 $files = getFiles(array_slice($argv, 1));
 foreach ($files as $path) {
     if (!preg_match('/^(.*)\.phpt$/', $path, $matches)) {
@@ -78,6 +92,11 @@ function normalizeOutput(string $out): string {
     // any string. These tend to contain homedirs with usernames, not good.
     $out = preg_replace("/'(\/|[A-Z]:\\\\)\S+\\.\\.\\.'/", "'%s'", $out);
     $out = preg_replace("/'file:(\/|[A-Z]:\\\\)\S+\\.\\.\\.'/", "'%s'", $out);
+    // Replace system error strings for portability.
+    global $strerrors;
+    foreach ($strerrors as $strerror) {
+        $out = str_replace($strerror, "%s", $out);
+    }
     $out = str_replace("\0", '%0', $out);
     return $out;
 }