diff --git a/lib/iscsi/iscsi.c b/lib/iscsi/iscsi.c
index b1bc43119..b3cf2e8b1 100644
--- a/lib/iscsi/iscsi.c
+++ b/lib/iscsi/iscsi.c
@@ -4649,8 +4649,6 @@ spdk_iscsi_read_pdu(struct spdk_iscsi_conn *conn, struct spdk_iscsi_pdu **_pdu)
 		}
 	}
 
-	data_len = ISCSI_ALIGN(DGET24(pdu->bhs.data_segment_len));
-
 	/* AHS */
 	ahs_len = pdu->bhs.total_ahs_len * 4;
 	assert(ahs_len <= ISCSI_AHS_LEN);
@@ -4684,6 +4682,8 @@ spdk_iscsi_read_pdu(struct spdk_iscsi_conn *conn, struct spdk_iscsi_pdu **_pdu)
 		}
 	}
 
+	data_len = ISCSI_ALIGN(DGET24(pdu->bhs.data_segment_len));
+
 	/* copy the actual data into local buffer */
 	if (pdu->data_valid_bytes < data_len) {
 		if (pdu->data_buf == NULL) {