diff --git a/ultramodern/src/renderer_context.cpp b/ultramodern/src/renderer_context.cpp
index 909fdee..bd796c5 100644
--- a/ultramodern/src/renderer_context.cpp
+++ b/ultramodern/src/renderer_context.cpp
@@ -1,4 +1,5 @@
 #include <cassert>
+#include <mutex>
 
 #include "ultramodern/renderer_context.hpp"
 #include "ultramodern/ultramodern.hpp"