diff --git a/lib/antlr/antlr/CharScanner.h b/lib/antlr/antlr/CharScanner.h
index e553d64d..2e2ffc7c 100644
--- a/lib/antlr/antlr/CharScanner.h
+++ b/lib/antlr/antlr/CharScanner.h
@@ -10,6 +10,7 @@
 
 #include <antlr/config.h>
 
+#include <functional>
 #include <map>
 
 #ifdef HAS_NOT_CCTYPE_H