diff --git a/extras/audio plugins/wrapper/formats/AudioUnit/juce_AudioUnitWrapper.cpp b/extras/audio plugins/wrapper/formats/AudioUnit/juce_AudioUnitWrapper.cpp
index 63df2b2c05..282c5dfb00 100644
--- a/extras/audio plugins/wrapper/formats/AudioUnit/juce_AudioUnitWrapper.cpp	
+++ b/extras/audio plugins/wrapper/formats/AudioUnit/juce_AudioUnitWrapper.cpp	
@@ -780,7 +780,7 @@ private:
     SMPTETime lastSMPTETime;
     AUChannelInfo channelInfo [numChannelConfigs];
     AudioUnitEvent auEvent;
-    MemoryBlock presetsArray;
+    mutable MemoryBlock presetsArray;
 };