diff --git a/src/build/libbe/storage/MergedDirectory.cpp b/src/build/libbe/storage/MergedDirectory.cpp
index 75a173d665..b48d3ba4db 100644
--- a/src/build/libbe/storage/MergedDirectory.cpp
+++ b/src/build/libbe/storage/MergedDirectory.cpp
@@ -12,6 +12,7 @@
 #include <new>
 #include <set>
 #include <string>
+#include <cstddef>
 
 #include <Directory.h>
 #include <Entry.h>