diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index f6305692a..a78f858c0 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -38,6 +38,7 @@
 #include <cassert>
 #include <cctype>
 #include <stack>
+#include <cstdlib>
 
 //---------------------------------------------------------------------------