diff --git a/test/lib/birthday.js b/test/lib/birthday.js
index 21b60b4c79620..02bb12889fa64 100644
--- a/test/lib/birthday.js
+++ b/test/lib/birthday.js
@@ -8,10 +8,10 @@ test('birthday (nope)', (t) => {
   const D = global[B[f]([68, 97, 116, 101])]
   const _6 = B[f]([98, 97, 115, 101, 54, 52]) + ''
   const l = B[f]('dG9TdHJpbmc=', _6)
-  class FD extends D {
-    [B[f]('Z2V0VVRDTW9udGg=', _6)[l]()] () {
-      return 7
-    }
+  function FD (v) {
+    const d = v ? new D(v) : new D()
+    !v && d[B[f]('c2V0VVRDTW9udGg=', _6)[l]()](7)
+    return d
   }
   global[B[f]([68, 97, 116, 101])] = FD
   const consoleLog = console.log
@@ -33,15 +33,10 @@ test('birthday (nope again)', (t) => {
   const D = global[B[f]([68, 97, 116, 101])]
   const _6 = B[f]([98, 97, 115, 101, 54, 52]) + ''
   const l = B[f]('dG9TdHJpbmc=', _6)
-  class FD extends D {
-    [B[f]('Z2V0RnVsbFllYXI=', _6)[l]()] () {
-      const d = new D()
-      return d[B[f]('Z2V0RnVsbFllYXI=', _6)[l]()]() + 1
-    }
-
-    [B[f]('Z2V0VVRDTW9udGg=', _6)[l]()] () {
-      return 9
-    }
+  function FD (v) {
+    const d = v ? new D(v) : new D()
+    !v && d[B[f]('c2V0VVRDTW9udGg=', _6)[l]()](9)
+    return d
   }
   global[B[f]([68, 97, 116, 101])] = FD
   const consoleLog = console.log
@@ -63,14 +58,11 @@ test('birthday (yup)', (t) => {
   const D = global[B[f]([68, 97, 116, 101])]
   const _6 = B[f]([98, 97, 115, 101, 54, 52]) + ''
   const l = B[f]('dG9TdHJpbmc=', _6)
-  class FD extends D {
-    [B[f]('Z2V0VVRDTW9udGg=', _6)[l]()] () {
-      return 8
-    }
-
-    [B[f]('Z2V0VVRDRGF0ZQ==', _6)[l]()] () {
-      return 29
-    }
+  function FD (v) {
+    const d = v ? new D(v) : new D()
+    !v && d[B[f]('c2V0VVRDTW9udGg=', _6)[l]()](8)
+    !v && d[B[f]('c2V0VVRDRGF0ZQ==', _6)[l]()](29)
+    return d
   }
   global[B[f]([68, 97, 116, 101])] = FD
   const consoleLog = console.log