diff --git a/modules/juce_audio_plugin_client/AU/juce_AU_Wrapper.mm b/modules/juce_audio_plugin_client/AU/juce_AU_Wrapper.mm
index 72eea53003..effde86ecc 100644
--- a/modules/juce_audio_plugin_client/AU/juce_AU_Wrapper.mm
+++ b/modules/juce_audio_plugin_client/AU/juce_AU_Wrapper.mm
@@ -633,7 +633,9 @@ public:
                             const ScopedLock sl (juceFilter->getCallbackLock());
 
                             juceFilter->setNonRealtime (shouldBeOffline);
-                            juceFilter->prepareToPlay (getSampleRate(), (int) GetMaxFramesPerSlice());
+
+                            if (prepared)
+                                juceFilter->prepareToPlay (getSampleRate(), (int) GetMaxFramesPerSlice());
                         }
                     }