diff --git a/src/libutil/json.cc b/src/libutil/json.cc
index 0a6fb65f0..f80726d26 100644
--- a/src/libutil/json.cc
+++ b/src/libutil/json.cc
@@ -1,6 +1,7 @@
 #include "json.hh"
 
 #include <iomanip>
+#include <cstdint>
 #include <cstring>
 
 namespace nix {