diff --git a/src/apps/altcp_tls/altcp_tls_mbedtls.c b/src/apps/altcp_tls/altcp_tls_mbedtls.c
index 7e61bae0..466be388 100644
--- a/src/apps/altcp_tls/altcp_tls_mbedtls.c
+++ b/src/apps/altcp_tls/altcp_tls_mbedtls.c
@@ -894,6 +894,11 @@ altcp_mbedtls_close(struct altcp_pcb *conn)
   }
   state = (altcp_mbedtls_state_t *)conn->state;
   if (state != NULL) {
+    if (state->rx) {
+      /* free leftover (unhandled) rx pbufs */
+      pbuf_free(state->rx);
+      state->rx = NULL;
+    }
     state->flags |= ALTCP_MBEDTLS_FLAGS_TX_CLOSED;
     if (state->flags & ALTCP_MBEDTLS_FLAGS_RX_CLOSED) {
       altcp_mbedtls_dealloc(conn);