diff --git a/src/scanner.c b/src/scanner.c
index 471b507..9fa08c3 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -31,6 +31,7 @@
 
 #include <stdlib.h>
 #include <wchar.h>
+#include <wctype.h>
 
 #include "tree_sitter/parser.h"
 #include "tree_sitter/alloc.h"