diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 1f37904d073cf793f58267c778a7c46e10beb900..a3fb34c23bd3e876769d7ab0f17cefb42338eecb 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -4123,7 +4123,7 @@ static void __get_from_jb(const void *p)
 	if(ms >= (next = jb_next(pvt->jb))) {
 		struct ast_format *voicefmt;
 		voicefmt = ast_format_compatibility_bitfield2format(pvt->voiceformat);
-		ret = jb_get(pvt->jb, &frame, ms, ast_format_get_default_ms(voicefmt));
+		ret = jb_get(pvt->jb, &frame, ms, voicefmt ? ast_format_get_default_ms(voicefmt) : 20);
 		switch(ret) {
 		case JB_OK:
 			fr = frame.data;