diff --git a/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp b/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
index 6d289d114e..a9e4f82867 100644
--- a/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
+++ b/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
@@ -642,8 +642,6 @@ void AudioThumbnail::saveTo (OutputStream& output) const
 //==============================================================================
 bool AudioThumbnail::setDataSource (LevelDataSource* newSource)
 {
-    JUCE_ASSERT_MESSAGE_MANAGER_IS_LOCKED
-
     numSamplesFinished = 0;
     auto wasSuccessful = [&] { return sampleRate > 0 && totalSamples > 0; };