diff --git a/modules/juce_audio_devices/native/juce_mac_CoreAudio.cpp b/modules/juce_audio_devices/native/juce_mac_CoreAudio.cpp
index 2a9ee77f34..2682be4f06 100644
--- a/modules/juce_audio_devices/native/juce_mac_CoreAudio.cpp
+++ b/modules/juce_audio_devices/native/juce_mac_CoreAudio.cpp
@@ -1328,7 +1328,7 @@ private:
         inputChans.add (nullptr);
         outputChans.add (nullptr);
 
-        const int blockSizeMs = jmax (1, (int) (numSamples / currentSampleRate));
+        const int blockSizeMs = jmax (1, (int) (1000 * numSamples / currentSampleRate));
 
         jassert (numInputChans + numOutputChans == buffer.getNumChannels());