diff --git a/meta.c b/meta.c
index 30c9693..3cbc900 100644
--- a/meta.c
+++ b/meta.c
@@ -73,6 +73,8 @@ int main() {
         {"RSHIFT",            ">>"},
     };
 
+    printf("// auto generated by meta.c\n");
+
     printf("typedef enum {\n");
     for (int i = 0; i < ilen(kinds); i += 1) {
         printf("    TOK_%s,\n", kinds[i].name);
diff --git a/meta_gen.c b/meta_gen.c
index e98a878..5ca6a54 100644
--- a/meta_gen.c
+++ b/meta_gen.c
@@ -1,3 +1,4 @@
+// auto generated by meta.c
 typedef enum {
     TOK_EOF,
     TOK_ERROR,