diff --git a/cpu/stm32/periph/timer.c b/cpu/stm32/periph/timer.c
index 6f5004177a..92660fa755 100644
--- a/cpu/stm32/periph/timer.c
+++ b/cpu/stm32/periph/timer.c
@@ -267,7 +267,12 @@ static inline void irq_handler(tim_t tim)
 {
     uint32_t top = dev(tim)->ARR;
     uint32_t status = dev(tim)->SR & dev(tim)->DIER;
-    dev(tim)->SR = 0;
+
+    /* clear interrupts which we are about to service */
+    /* Note, the flags in the SR register can be cleared by software, but
+     * setting them has no effect on the register. Only the hardware can set
+     * them. */
+    dev(tim)->SR = ~status;
 
     for (unsigned int i = 0; status; i++) {
         uint32_t msk = TIM_SR_CC1IF << i;
diff --git a/sys/net/application_layer/cord/ep/cord_ep.c b/sys/net/application_layer/cord/ep/cord_ep.c
index 36b618c714..4bc13538fa 100644
--- a/sys/net/application_layer/cord/ep/cord_ep.c
+++ b/sys/net/application_layer/cord/ep/cord_ep.c
@@ -151,8 +151,10 @@ static int _update_remove(unsigned code, gcoap_resp_handler_t handle)
     ssize_t pkt_len = coap_opt_finish(&pkt, COAP_OPT_FINISH_NONE);
 
     /* send request */
-    gcoap_req_send(buf, pkt_len, &_rd_remote, handle, NULL);
-
+    ssize_t send_len = gcoap_req_send(buf, pkt_len, &_rd_remote, handle, NULL);
+    if (send_len <= 0) {
+        return CORD_EP_ERR;
+    }
     /* synchronize response */
     return _sync();
 }
@@ -224,7 +226,7 @@ static int _discover_internal(const sock_udp_ep_t *remote,
     coap_opt_add_uri_query(&pkt, "rt", "core.rd");
     size_t pkt_len = coap_opt_finish(&pkt, COAP_OPT_FINISH_NONE);
     res = gcoap_req_send(buf, pkt_len, remote, _on_discover, NULL);
-    if (res < 0) {
+    if (res <= 0) {
         return CORD_EP_ERR;
     }
     return _sync();
@@ -295,7 +297,7 @@ int cord_ep_register(const sock_udp_ep_t *remote, const char *regif)
 
     /* send out the request */
     res = gcoap_req_send(buf, pkt_len, remote, _on_register, NULL);
-    if (res < 0) {
+    if (res <= 0) {
         retval = CORD_EP_ERR;
         goto end;
     }