diff --git a/src/audio_core/cubeb_sink.cpp b/src/audio_core/cubeb_sink.cpp
index e679a95886..699f5b47c8 100644
--- a/src/audio_core/cubeb_sink.cpp
+++ b/src/audio_core/cubeb_sink.cpp
@@ -2,6 +2,7 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <mutex>
 #include <vector>
 #include <cubeb/cubeb.h>
 #include "audio_core/audio_types.h"
@@ -17,6 +18,7 @@ struct CubebSink::Impl {
     cubeb* ctx = nullptr;
     cubeb_stream* stream = nullptr;
 
+    std::mutex queue_mutex;
     std::vector<s16> queue;
 
     static long DataCallback(cubeb_stream* stream, void* user_data, const void* input_buffer,
@@ -97,6 +99,8 @@ void CubebSink::EnqueueSamples(const s16* samples, size_t sample_count) {
     if (!impl->ctx)
         return;
 
+    std::lock_guard lock{impl->queue_mutex};
+
     impl->queue.reserve(impl->queue.size() + sample_count * 2);
     std::copy(samples, samples + sample_count * 2, std::back_inserter(impl->queue));
 }
@@ -105,6 +109,7 @@ size_t CubebSink::SamplesInQueue() const {
     if (!impl->ctx)
         return 0;
 
+    std::lock_guard lock{impl->queue_mutex};
     return impl->queue.size() / 2;
 }
 
@@ -116,6 +121,8 @@ long CubebSink::Impl::DataCallback(cubeb_stream* stream, void* user_data, const
     if (!impl)
         return 0;
 
+    std::lock_guard lock{impl->queue_mutex};
+
     size_t frames_to_write = std::min(impl->queue.size() / 2, static_cast<size_t>(num_frames));
 
     memcpy(buffer, impl->queue.data(), frames_to_write * sizeof(s16) * 2);