diff --git a/main.c b/main.c
index 087daeb..35c5b97 100644
--- a/main.c
+++ b/main.c
@@ -41,6 +41,11 @@ enum	page {
 	PAGE__MAX
 };
 
+enum key {
+  KEY_ID,
+  KEY__MAX
+};
+
 static const char *const pages[PAGE__MAX] = {
 	"index", /* PAGE_INDEX */
 	"books", /* PAGE_BOOKS */
@@ -48,6 +53,10 @@ static const char *const pages[PAGE__MAX] = {
 	"series", /* PAGE_SERIES */
 };
 
+static const struct kvalid keys[KEY__MAX] = {
+  { kvalid_int, "id" }, /* KEY_ID */
+};
+
 /*
  * Fill out all HTTP secure headers.
  * Use the existing document's MIME type.
@@ -86,6 +95,9 @@ sendbooks(struct kreq *r)
   kjson_open(&req, r);
   kjson_obj_open(&req);
   kjson_putstringp(&req, "data", "books");
+  if (NULL != r->fieldmap[KEY_ID]) {
+    kjson_putintp(&req, "id", r->fieldmap[KEY_ID]->parsed.i);
+  }
   kjson_obj_close(&req);
   kjson_close(&req);
 }
@@ -138,7 +150,7 @@ main(void)
 	/* Actually parse HTTP document. */
 
 	er = khttp_parsex(&r, ksuffixmap, 
-          kmimetypes, KMIME__MAX, NULL, 0, 
+          kmimetypes, KMIME__MAX, keys, KEY__MAX,
           pages, PAGE__MAX, KMIME_APP_JSON, 
           PAGE_INDEX, NULL, NULL, 0, NULL);