diff --git a/spec/tests/test-hyperscript-behavioral.sx b/spec/tests/test-hyperscript-behavioral.sx
index 3b7255c2..6db20056 100644
--- a/spec/tests/test-hyperscript-behavioral.sx
+++ b/spec/tests/test-hyperscript-behavioral.sx
@@ -1172,7 +1172,7 @@
     ))
   (deftest "can call global javascript functions"
     (hs-cleanup!)
-    (host-set! (host-global "window") "calledWith" null)
+    (host-set! (host-global "window") "calledWith" nil)
     (let ((_el-div (dom-create-element "div")))
       (dom-set-attr _el-div "_" "on click call globalFunction(\"foo\")")
       (dom-append (dom-body) _el-div)
diff --git a/tests/hs-run-filtered.js b/tests/hs-run-filtered.js
index a3978dce..ff2b6231 100755
--- a/tests/hs-run-filtered.js
+++ b/tests/hs-run-filtered.js
@@ -399,6 +399,8 @@ globalThis.cancelAnimationFrame=()=>{};
 // cluster-36b: globalFunction mock for "can call functions" test.
 // The test calls globalFunction("foo") via hyperscript and checks window.calledWith.
 globalThis.globalFunction = function(x) { globalThis.calledWith = x; };
+// asyncCheck: async-when test needs a truthy-returning global (simulates async guard).
+globalThis.asyncCheck = function() { return true; };
 // cluster-asyncError: function that returns a rejected promise.
 globalThis.failAsync = function() { return Promise.reject(new Error("boom")); };
 // HsMutationObserver — cluster-32 mutation mock. Maintains a global
diff --git a/tests/playwright/generate-sx-tests.py b/tests/playwright/generate-sx-tests.py
index 718a9131..2f7cf5f0 100644
--- a/tests/playwright/generate-sx-tests.py
+++ b/tests/playwright/generate-sx-tests.py
@@ -1881,6 +1881,14 @@ def js_expr_to_sx(expr):
     if m:
         return f'(host-get {m.group(1)} "{m.group(2)}")'
 
+    # JS keywords / literals
+    if expr in ('null', 'undefined'):
+        return 'nil'
+    if expr == 'true':
+        return 'true'
+    if expr == 'false':
+        return 'false'
+
     # Bare identifier
     if re.match(r'^[A-Za-z_]\w*$', expr):
         return expr