diff --git a/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp b/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
index 74d7ca4681..b7a8758bf9 100644
--- a/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
+++ b/modules/juce_audio_utils/gui/juce_AudioThumbnail.cpp
@@ -710,8 +710,6 @@ 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; };