diff --git a/pjmedia/src/pjmedia-audiodev/pa_dev.c b/pjmedia/src/pjmedia-audiodev/pa_dev.c
index 06d273c..0a0e7a2 100644
--- a/pjmedia/src/pjmedia-audiodev/pa_dev.c
+++ b/pjmedia/src/pjmedia-audiodev/pa_dev.c
@@ -685,6 +685,8 @@
     const PaStreamInfo *paSI;
     PaError err;
 
+    PJ_ASSERT_RETURN(rec_cb && p_snd_strm, PJ_EINVAL);
+
     rec_id = param->rec_id;
     if (rec_id < 0) {
 	rec_id = pa_get_default_input_dev(param->channel_count);
@@ -788,6 +790,8 @@
     unsigned paFrames, paRate, paLatency;
     PaError err;
 
+    PJ_ASSERT_RETURN(play_cb && p_snd_strm, PJ_EINVAL);
+
     play_id = param->play_id;
     if (play_id < 0) {
 	play_id = pa_get_default_output_dev(param->channel_count);
@@ -898,6 +902,8 @@
     unsigned paFrames, paRate, paInputLatency, paOutputLatency;
     PaError err;
 
+    PJ_ASSERT_RETURN(play_cb && rec_cb && p_snd_strm, PJ_EINVAL);
+
     rec_id = param->rec_id;
     if (rec_id < 0) {
 	rec_id = pa_get_default_input_dev(param->channel_count);