diff --git a/Sources/IO/IOStream.swift b/Sources/IO/IOStream.swift
index a6a5ce8d5..b42eb43b8 100644
--- a/Sources/IO/IOStream.swift
+++ b/Sources/IO/IOStream.swift
@@ -185,10 +185,12 @@ open class IOStream: NSObject {
     /// Specifies the audio mixer settings.
     public var audioMixerSettings: IOAudioMixerSettings {
         get {
-            mixer.audioIO.mixerSettings
+            mixer.audioIO.lockQueue.sync { self.mixer.audioIO.mixerSettings }
         }
         set {
-            mixer.audioIO.mixerSettings = newValue
+            mixer.audioIO.lockQueue.async {
+                self.mixer.audioIO.mixerSettings = newValue
+            }
         }
     }