diff --git a/src/common/util.h b/src/common/util.h
index 93f32f48a2a6..85db7f387093 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -35,6 +35,7 @@
 #include <sstream>
 #include <algorithm>
 #include <array>
+#include <cctype>
 #include <memory>
 
 namespace tvm {