diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
index fe0a21a51..309d726e8 100644
--- a/src/modules/alsa/alsa-sink.c
+++ b/src/modules/alsa/alsa-sink.c
@@ -1203,6 +1203,9 @@ static int sink_process_msg(pa_msgobject *o, int code, void *data, int64_t offse
 
                     if (u->sink->thread_info.state == PA_SINK_INIT) {
                         if (build_pollfd(u) < 0)
+                            /* FIXME: This will cause an assertion failure in
+                             * pa_sink_put(), because with the current design
+                             * pa_sink_put() is not allowed to fail. */
                             return -PA_ERR_IO;
                     }
 
diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index b11a03f8d..adaa42cb3 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -1058,6 +1058,9 @@ static int source_process_msg(pa_msgobject *o, int code, void *data, int64_t off
 
                     if (u->source->thread_info.state == PA_SOURCE_INIT) {
                         if (build_pollfd(u) < 0)
+                            /* FIXME: This will cause an assertion failure in
+                             * pa_source_put(), because with the current design
+                             * pa_source_put() is not allowed to fail. */
                             return -PA_ERR_IO;
                     }