diff --git a/src/libutil/json.cc b/src/libutil/json.cc
index 3a981376f..b0a5d7e75 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 {