diff --git a/lib/src/phy/rf/rf_utils.c b/lib/src/phy/rf/rf_utils.c
index 24a47db7f..2f4e661bc 100644
--- a/lib/src/phy/rf/rf_utils.c
+++ b/lib/src/phy/rf/rf_utils.c
@@ -79,11 +79,11 @@ free_and_exit:
   return ret;
 }
 
-int srslte_rf_recv_wrapper_cs(void* h, cf_t* data[SRSLTE_MAX_CHANNELS], uint32_t nsamples, srslte_timestamp_t* t)
+int srslte_rf_recv_wrapper_cs(void* h, cf_t* data[SRSLTE_MAX_PORTS], uint32_t nsamples, srslte_timestamp_t* t)
 {
   DEBUG(" ----  Receive %d samples  ---- \n", nsamples);
-  void* ptr[SRSLTE_MAX_CHANNELS];
-  for (int i = 0; i < SRSLTE_MAX_CHANNELS; i++) {
+  void* ptr[SRSLTE_MAX_CHANNELS] = {};
+  for (int i = 0; i < SRSLTE_MAX_PORTS; i++) {
     ptr[i] = data[i];
   }
   return srslte_rf_recv_with_time_multi(h, ptr, nsamples, 1, NULL, NULL);
diff --git a/lib/src/phy/ue/ue_sync_nbiot.c b/lib/src/phy/ue/ue_sync_nbiot.c
index f459c722d..2f279d7e2 100644
--- a/lib/src/phy/ue/ue_sync_nbiot.c
+++ b/lib/src/phy/ue/ue_sync_nbiot.c
@@ -483,6 +483,9 @@ static int receive_samples(srslte_nbiot_ue_sync_t* q, cf_t* input_buffer[SRSLTE_
     ptr[i] = &input_buffer[i][q->next_rf_sample_offset];
   }
 
+  // assure  next_rf_sample_offset isn't larger than frame_len
+  q->next_rf_sample_offset = SRSLTE_MIN(q->next_rf_sample_offset, q->frame_len);
+
   if (q->recv_callback(q->stream, ptr, q->frame_len - q->next_rf_sample_offset, &q->last_timestamp) < 0) {
     return SRSLTE_ERROR;
   }