diff --git a/src/io/FileReader.hxx b/src/io/FileReader.hxx
index 6f1a34923..935c79f6f 100644
--- a/src/io/FileReader.hxx
+++ b/src/io/FileReader.hxx
@@ -42,6 +42,8 @@
 #include "io/UniqueFileDescriptor.hxx"
 #endif
 
+#include <cstdint>
+
 class Path;
 class FileInfo;