diff --git a/doc/newsfragments/gcc-11-build.bugfix b/doc/newsfragments/gcc-11-build.bugfix
new file mode 100644
index 00000000..255f5365
--- /dev/null
+++ b/doc/newsfragments/gcc-11-build.bugfix
@@ -0,0 +1 @@
+Fixed build on GCC 11.2 (https://github.com/debauchee/barrier/issues/1366).
diff --git a/src/lib/base/Event.h b/src/lib/base/Event.h
index 38a2cf11..cb00dccb 100644
--- a/src/lib/base/Event.h
+++ b/src/lib/base/Event.h
@@ -21,6 +21,8 @@
 #include "common/basic_types.h"
 #include "common/stdmap.h"
 
+#include <cstddef>
+
 class EventData {
 public:
     EventData() { }