diff --git a/src/rspro_util.c b/src/rspro_util.c
index 1369c77..c312e42 100644
--- a/src/rspro_util.c
+++ b/src/rspro_util.c
@@ -37,6 +37,7 @@
 
 	rval = der_encode_to_buffer(&asn_DEF_RsproPDU, pdu, msgb_data(msg), msgb_tailroom(msg));
 	if (rval.encoded < 0) {
+		fprintf(stderr, "Failed to encode %s\n", rval.failed_type->name);
 		return NULL;
 	}
 	msgb_put(msg, rval.encoded);