diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index dccd6faeef5330..83efaab210ea6f 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -826,7 +826,9 @@ void IndexOfString(const FunctionCallbackInfo<Value>& args) {
 
   Local<String> needle = args[1].As<String>();
   const char* haystack = ts_obj_data;
-  const size_t haystack_length = ts_obj_length;
+  // Round down to the nearest multiple of 2 in case of UCS2.
+  const size_t haystack_length = (enc == UCS2) ?
+      ts_obj_length &~ 1 : ts_obj_length;  // NOLINT(whitespace/operators)
 
   const size_t needle_length =
       StringBytes::Size(args.GetIsolate(), needle, enc);
diff --git a/test/parallel/test-buffer-indexof.js b/test/parallel/test-buffer-indexof.js
index b085b4b1ea66ff..06dfc3af0896c5 100644
--- a/test/parallel/test-buffer-indexof.js
+++ b/test/parallel/test-buffer-indexof.js
@@ -239,6 +239,9 @@ assert.strictEqual(new Buffer('aaaa').indexOf('a'.repeat(4), 'ucs2'), -1);
 assert.strictEqual(new Buffer('aaaa').indexOf('a'.repeat(4), 'utf8'), 0);
 assert.strictEqual(new Buffer('aaaa').indexOf('你好', 'ucs2'), -1);
 
+// Haystack has odd length, but the needle is UCS2.
+assert.strictEqual(new Buffer('aaaaa').indexOf('b', 'ucs2'), -1);
+
 {
   // Find substrings in Utf8.
   const lengths = [1, 3, 15];  // Single char, simple and complex.