diff --git a/lib/dns/include/dns/qp.h b/lib/dns/include/dns/qp.h
index b089cc7db5..5e9a1f25a1 100644
--- a/lib/dns/include/dns/qp.h
+++ b/lib/dns/include/dns/qp.h
@@ -193,8 +193,9 @@ typedef uint8_t dns_qpkey_t[512];
  *
  * The `makekey` method fills in a `dns_qpkey_t` corresponding to a
  * value object stored in the qp-trie. It returns the length of the
- * key. This method will typically call dns_qpkey_fromname() with a
- * name stored in the value object.
+ * key, which must be less than `sizeof(dns_qpkey_t)`. This method
+ * will typically call dns_qpkey_fromname() with a name stored in the
+ * value object.
  *
  * For logging and tracing, the `triename` method copies a human-
  * readable identifier into `buf` which has max length `size`.
@@ -395,15 +396,18 @@ dns_qpkey_fromname(dns_qpkey_t key, const dns_name_t *name);
  * Requires:
  * \li  `name` is a pointer to a valid `dns_name_t`
  *
+ * Ensures:
+ * \li	returned length is less than `sizeof(dns_qpkey_t)`
+ *
  * Returns:
  * \li  the length of the key
  */
 
 isc_result_t
-dns_qp_getkey(dns_qpreadable_t qpr, const dns_qpkey_t searchk, size_t searchl,
-	      void **pval_r, uint32_t *ival_r);
+dns_qp_getkey(dns_qpreadable_t qpr, const dns_qpkey_t search_key,
+	      size_t search_keylen, void **pval_r, uint32_t *ival_r);
 /*%<
- * Find a leaf in a qp-trie that matches the given key
+ * Find a leaf in a qp-trie that matches the given search key
  *
  * The leaf values are assigned to `*pval_r` and `*ival_r`
  *
@@ -411,6 +415,7 @@ dns_qp_getkey(dns_qpreadable_t qpr, const dns_qpkey_t searchk, size_t searchl,
  * \li  `qpr` is a pointer to a readable qp-trie
  * \li  `pval_r != NULL`
  * \li  `ival_r != NULL`
+ * \li	`search_keylen < sizeof(dns_qpkey_t)`
  *
  * Returns:
  * \li  ISC_R_NOTFOUND if the trie has no leaf with a matching key
@@ -452,12 +457,13 @@ dns_qp_insert(dns_qp_t *qp, void *pval, uint32_t ival);
  */
 
 isc_result_t
-dns_qp_deletekey(dns_qp_t *qp, const dns_qpkey_t key, size_t len);
+dns_qp_deletekey(dns_qp_t *qp, const dns_qpkey_t key, size_t keylen);
 /*%<
  * Delete a leaf from a qp-trie that matches the given key
  *
  * Requires:
  * \li  `qp` is a pointer to a valid qp-trie
+ * \li	`keylen < sizeof(dns_qpkey_t)`
  *
  * Returns:
  * \li  ISC_R_NOTFOUND if the trie has no leaf with a matching key
diff --git a/lib/dns/qp.c b/lib/dns/qp.c
index 9c02c94619..e990a61e3f 100644
--- a/lib/dns/qp.c
+++ b/lib/dns/qp.c
@@ -242,6 +242,7 @@ dns_qpkey_fromname(dns_qpkey_t key, const dns_name_t *name) {
 	}
 	/* mark end with a double NOBYTE */
 	key[len] = SHIFT_NOBYTE;
+	ENSURE(len < sizeof(dns_qpkey_t));
 	return (len);
 }
 
@@ -1606,6 +1607,7 @@ dns_qp_deletekey(dns_qp_t *qp, const dns_qpkey_t search_key,
 	qp_node_t *n;
 
 	REQUIRE(QP_VALID(qp));
+	REQUIRE(search_keylen < sizeof(dns_qpkey_t));
 
 	if (get_root(qp) == NULL) {
 		return (ISC_R_NOTFOUND);
@@ -1696,6 +1698,7 @@ dns_qp_getkey(dns_qpreadable_t qpr, const dns_qpkey_t search_key,
 	REQUIRE(QP_VALID(qp));
 	REQUIRE(pval_r != NULL);
 	REQUIRE(ival_r != NULL);
+	REQUIRE(search_keylen < sizeof(dns_qpkey_t));
 
 	n = get_root(qp);
 	if (n == NULL) {
diff --git a/lib/dns/qp_p.h b/lib/dns/qp_p.h
index 6f9084e831..183335e4e4 100644
--- a/lib/dns/qp_p.h
+++ b/lib/dns/qp_p.h
@@ -937,8 +937,10 @@ detach_leaf(dns_qpreadable_t qpr, qp_node_t *n) {
 static inline size_t
 leaf_qpkey(dns_qpreadable_t qpr, qp_node_t *n, dns_qpkey_t key) {
 	dns_qpreader_t *qp = dns_qpreader(qpr);
-	return (qp->methods->makekey(key, qp->uctx, leaf_pval(n),
-				     leaf_ival(n)));
+	size_t len = qp->methods->makekey(key, qp->uctx, leaf_pval(n),
+					  leaf_ival(n));
+	INSIST(len < sizeof(dns_qpkey_t));
+	return (len);
 }
 
 static inline char *