diff --git a/include/orcus/json_document_tree.hpp b/include/orcus/json_document_tree.hpp
index e558c38..9942ed8 100644
--- a/include/orcus/json_document_tree.hpp
+++ b/include/orcus/json_document_tree.hpp
@@ -14,6 +14,7 @@
 #include <string>
 #include <memory>
 #include <vector>
+#include <cstdint>
 
 namespace orcus {
 
diff --git a/include/orcus/sax_parser.hpp b/include/orcus/sax_parser.hpp
index f7283d2..5f42e2f 100644
--- a/include/orcus/sax_parser.hpp
+++ b/include/orcus/sax_parser.hpp
@@ -11,6 +11,7 @@
 #include "sax_parser_base.hpp"
 
 #include <string_view>
+#include <cstdint>
 
 namespace orcus {
 
diff --git a/include/orcus/yaml_document_tree.hpp b/include/orcus/yaml_document_tree.hpp
index d22a588..886881f 100644
--- a/include/orcus/yaml_document_tree.hpp
+++ b/include/orcus/yaml_document_tree.hpp
@@ -14,6 +14,7 @@
 #include <string>
 #include <memory>
 #include <vector>
+#include <cstdint>
 
 namespace orcus {
 
diff --git a/include/orcus/zip_archive.hpp b/include/orcus/zip_archive.hpp
index afc6727..aac5e4b 100644
--- a/include/orcus/zip_archive.hpp
+++ b/include/orcus/zip_archive.hpp
@@ -15,6 +15,7 @@
 #include <vector>
 #include <memory>
 #include <ostream>
+#include <cstdint>
 
 namespace orcus {