diff --git a/src/include/tokenize.h b/src/include/tokenize.h
index 8934a75..4e42b0f 100644
--- a/src/include/tokenize.h
+++ b/src/include/tokenize.h
@@ -1,3 +1,6 @@
+#ifndef TOKENIZE_H
+#define TOKENIZE_H
+
 #include <vector>
 using namespace std;
 
@@ -12,4 +15,6 @@ union TokenData {
 struct Token {
     TokenType type;
     TokenData data;
-};
\ No newline at end of file
+};
+
+#endif
\ No newline at end of file