diff --git a/simap.h b/simap.h
index 25ddc53..319bc20 100644
--- a/simap.h
+++ b/simap.h
@@ -1,9 +1,9 @@
 #ifndef SIMAP_H
 #define SIMAP_H
-#include <stddef.h>
-#include <stdint.h>
-#include <string.h>
-#include <assert.h>
+#include <stddef.h> /* NULL */
+#include <stdint.h> /* uint8_t, uint32_t, ... */
+#include <string.h> /* strcmp, strncpy etc. */
+#include <assert.h> /* assert */
 #include "amap.h"
 #include "arena.h/arena.h"