diff --git a/tests/phpt/server/static/012-static-h2.phpt b/tests/phpt/server/static/012-static-h2.phpt
index 58927d7..eb79d46 100644
--- a/tests/phpt/server/static/012-static-h2.phpt
+++ b/tests/phpt/server/static/012-static-h2.phpt
@@ -58,11 +58,37 @@ $client = spawn(function() use ($port, $server, $body) {
          * separately so we can parse ":status" and Content-Length
          * cleanly even on 206 / 304. */
         $args = ['--http2-prior-knowledge', '-sS', '-i', '--max-time', '3'];
-        foreach ($extra_args as $a) $args[] = $a;
+
+        /* Route request headers through a curl --config file rather than
+         * shell-quoted -H. An ETag is `W/"hex"`, and PHP's escapeshellarg()
+         * on Windows cannot carry a double quote — it replaces every " with
+         * a space, so `If-None-Match: W/"hex"` would reach curl as
+         * `W/ hex `. Leading/trailing whitespace makes that a malformed
+         * HTTP/2 field value (RFC 9113 §8.2.1), which the server correctly
+         * rejects with a stream PROTOCOL_ERROR. curl config files use curl's
+         * own (shell-independent) quoting, so the quotes survive everywhere. */
+        $rest = []; $cfg_lines = []; $cfg = null;
+        for ($i = 0, $n = count($extra_args); $i < $n; $i++) {
+            if ($extra_args[$i] === '-H' && $i + 1 < $n) {
+                $val = $extra_args[++$i];
+                $esc = str_replace(['\\', '"'], ['\\\\', '\\"'], $val);
+                $cfg_lines[] = 'header = "' . $esc . '"';
+            } else {
+                $rest[] = $extra_args[$i];
+            }
+        }
+        if ($cfg_lines) {
+            $cfg = tempnam(sys_get_temp_dir(), 'h2cfg');
+            file_put_contents($cfg, implode("\n", $cfg_lines) . "\n");
+            $args[] = '--config';
+            $args[] = $cfg;
+        }
+        foreach ($rest as $a) $args[] = $a;
         $args[] = "http://127.0.0.1:$port$path";
         $cmd = 'curl ' . implode(' ', array_map('escapeshellarg', $args));
         $out = []; $rc = 0;
         exec($cmd . ' 2>&1', $out, $rc);
+        if ($cfg !== null) @unlink($cfg);
         $resp = implode("\n", $out);
         /* Parse a curl -i response: header block ends at the blank
          * line; HTTP/2 status line is "HTTP/2 NNN". */