diff --git a/smt/smt.h b/smt/smt.h
index 2af69b709..a33390539 100644
--- a/smt/smt.h
+++ b/smt/smt.h
@@ -3,6 +3,7 @@
 // Copyright (c) 2018-present The Alive2 Authors.
 // Distributed under the MIT license that can be found in the LICENSE file.
 
+#include <cstdint>
 #include <string>
 
 namespace smt {
diff --git a/tools/alive_lexer.h b/tools/alive_lexer.h
index 1fc9098d3..46ccb73ee 100644
--- a/tools/alive_lexer.h
+++ b/tools/alive_lexer.h
@@ -3,6 +3,7 @@
 // Copyright (c) 2018-present The Alive2 Authors.
 // Distributed under the MIT license that can be found in the LICENSE file.
 
+#include <cstdint>
 #include <string>
 #include <string_view>