diff --git a/man/coap_handler.txt.in b/man/coap_handler.txt.in
index b0e33888..044f122e 100644
--- a/man/coap_handler.txt.in
+++ b/man/coap_handler.txt.in
@@ -118,7 +118,8 @@ This _handler_ must not call *coap_send*(3) to send _response_pdu_.
 _response_pdu_ gets sent on return from _handler_, assuming the response
 code has been updated. If the response code was not updated, then an empty
 ACK packet will get sent for CON type requests or nothing for NON type
-requests.
+requests.  Nothing gets sent for a separate response (*coap_async*(3)), as
+an Empty message is only valid as an ACK or a RST.
 
 *NOTE:* Any data associated with _incoming_pdu_ is no longer be available after
 exiting this function as _incoming_pdu_ is deleted.  In particular
diff --git a/src/coap_net.c b/src/coap_net.c
index 97fac703..dc9e7eaa 100644
--- a/src/coap_net.c
+++ b/src/coap_net.c
@@ -3573,8 +3573,9 @@ enum respond_t { RESPONSE_DEFAULT, RESPONSE_DROP, RESPONSE_SEND };
  * change it to an empty ACK and @c RESPONSE_SEND so the client does not keep
  * on retrying.
  *
- * Checks if the response code is 0.00 and if either the session is reliable or
- * non-confirmable, @c RESPONSE_DROP is also returned.
+ * Checks if the response code is 0.00 and if the response is confirmable,
+ * non-confirmable, or the session is reliable, @c RESPONSE_DROP is also
+ * returned.  An Empty confirmable message is a ping, not a response.
  *
  * Multicast response checking is also carried out.
  *
@@ -3673,8 +3674,13 @@ no_response(coap_pdu_t *request, coap_pdu_t *response,
     }
   } else if (COAP_PDU_IS_EMPTY(response) &&
              (response->type == COAP_MESSAGE_NON ||
+              response->type == COAP_MESSAGE_CON ||
               COAP_PROTO_RELIABLE(session->proto))) {
-    /* response is 0.00, and this is reliable or non-confirmable */
+    /* Response is 0.00, and this is reliable, non-confirmable, or a separate
+     * (confirmable) response.  An Empty CON is a ping (RFC 7252 4.2), not a
+     * response, and the PDU still has the request's token attached, which
+     * RFC 7252 4.1 does not allow.  A CON would then get retransmitted up to
+     * MAX_RETRANSMIT times. */
     return RESPONSE_DROP;
   }
 
@@ -4352,6 +4358,7 @@ skip_handler:
     }
   } else if (COAP_PDU_IS_EMPTY(response) &&
              (response->type == COAP_MESSAGE_NON ||
+              response->type == COAP_MESSAGE_CON ||
               COAP_PROTO_RELIABLE(session->proto))) {
     coap_delete_pdu_lkd(response);
   } else {