diff --git a/Machines/Apple/Macintosh/Audio.cpp b/Machines/Apple/Macintosh/Audio.cpp
index a6dac5cd6..fba2c11ea 100644
--- a/Machines/Apple/Macintosh/Audio.cpp
+++ b/Machines/Apple/Macintosh/Audio.cpp
@@ -25,7 +25,7 @@ Audio::Audio(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(tas
 void Audio::post_sample(uint8_t sample) {
 	// Store sample directly indexed by current write pointer; this ensures that collected samples
 	// directly map to volume and enabled/disabled states.
-	sample_queue_.buffer[sample_queue_.write_pointer] = sample;
+	sample_queue_.buffer[sample_queue_.write_pointer].store(sample, std::memory_order::memory_order_relaxed);
 	sample_queue_.write_pointer = (sample_queue_.write_pointer + 1) % sample_queue_.buffer.size();
 }
 
@@ -80,7 +80,7 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 
 		// Determine the output level, and output that many samples.
 		// (Hoping that the copiler substitutes an effective memset16-type operation here).
-		const int16_t output_level = volume_multiplier_ * (int16_t(sample_queue_.buffer[sample_queue_.read_pointer]) - 128);
+		const int16_t output_level = volume_multiplier_ * (int16_t(sample_queue_.buffer[sample_queue_.read_pointer].load(std::memory_order::memory_order_relaxed)) - 128);
 		for(size_t c = 0; c < cycles_left_in_sample; ++c) {
 			target[c] = output_level;
 		}
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index 3d8f5835d..a0ae25a80 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -63,7 +63,7 @@ class Audio: public ::Outputs::Speaker::SampleSource {
 		// A queue of fetched samples; read from by one thread,
 		// written to by another.
 		struct {
-			std::array<uint8_t, 740> buffer;
+			std::array<std::atomic<uint8_t>, 740> buffer;
 			size_t read_pointer = 0, write_pointer = 0;
 		} sample_queue_;