diff --git a/test/parallel/test-buffer-includes.js b/test/parallel/test-buffer-includes.js
index 2a163f9e0c628e..605f988de5c648 100644
--- a/test/parallel/test-buffer-includes.js
+++ b/test/parallel/test-buffer-includes.js
@@ -214,8 +214,9 @@ assert(asciiString.includes('leb', 0));
 
 // Search in string containing many non-ASCII chars.
 const allCodePoints = [];
-for (let i = 0; i < 65536; i++) allCodePoints[i] = i;
-const allCharsString = String.fromCharCode.apply(String, allCodePoints);
+for (let i = 0; i < 65534; i++) allCodePoints[i] = i;
+const allCharsString = String.fromCharCode.apply(String, allCodePoints) +
+    String.fromCharCode(65534, 65535);
 const allCharsBufferUtf8 = Buffer.from(allCharsString);
 const allCharsBufferUcs2 = Buffer.from(allCharsString, 'ucs2');
 
diff --git a/test/parallel/test-buffer-indexof.js b/test/parallel/test-buffer-indexof.js
index cba6af44e5b02d..44353c127602d8 100644
--- a/test/parallel/test-buffer-indexof.js
+++ b/test/parallel/test-buffer-indexof.js
@@ -276,8 +276,9 @@ assert.strictEqual(asciiString.indexOf('leb', 0), 3);
 
 // Search in string containing many non-ASCII chars.
 const allCodePoints = [];
-for (let i = 0; i < 65536; i++) allCodePoints[i] = i;
-const allCharsString = String.fromCharCode.apply(String, allCodePoints);
+for (let i = 0; i < 65534; i++) allCodePoints[i] = i;
+const allCharsString = String.fromCharCode.apply(String, allCodePoints) +
+    String.fromCharCode(65534, 65535);
 const allCharsBufferUtf8 = Buffer.from(allCharsString);
 const allCharsBufferUcs2 = Buffer.from(allCharsString, 'ucs2');