diff --git a/lib/receiver.js b/lib/receiver.js
index e11e26618..2d29d62bb 100644
--- a/lib/receiver.js
+++ b/lib/receiver.js
@@ -417,7 +417,13 @@ class Receiver extends Writable {
       }
 
       data = this.consume(this._payloadLength);
-      if (this._masked) unmask(data, this._mask);
+
+      if (
+        this._masked &&
+        (this._mask[0] | this._mask[1] | this._mask[2] | this._mask[3]) !== 0
+      ) {
+        unmask(data, this._mask);
+      }
     }
 
     if (this._opcode > 0x07) return this.controlMessage(data);
diff --git a/lib/sender.js b/lib/sender.js
index 3ff623366..3e0058677 100644
--- a/lib/sender.js
+++ b/lib/sender.js
@@ -100,6 +100,10 @@ class Sender {
     target[offset - 2] = mask[2];
     target[offset - 1] = mask[3];
 
+    if ((mask[0] | mask[1] | mask[2] | mask[3]) === 0) {
+      return [target, data];
+    }
+
     if (merge) {
       applyMask(data, mask, target, offset, data.length);
       return [target];