diff --git a/camlibs/ptp2/ptp-pack.c b/camlibs/ptp2/ptp-pack.c
index 3af5b6bbb..26465efa3 100644
--- a/camlibs/ptp2/ptp-pack.c
+++ b/camlibs/ptp2/ptp-pack.c
@@ -2599,10 +2599,15 @@ ptp_unpack_CANON_changes (PTPParams *params, unsigned char* data, unsigned int d
 				 */
 				proptype = PTP_DPC_CANON_EOS_Aperture;
 				dpd = _lookup_or_allocate_canon_prop(params, proptype);
-				if (olcver >= 0x12)
-					dpd->CurrentValue.u16 = curdata[curoff+7]; /* CHECK */
-				else
+				if (olcver >= 0x12) {
+					if (olcver == 0x13) {
+						dpd->CurrentValue.u16 = curdata[curoff+7]; /* R5 */
+					} else {
+						dpd->CurrentValue.u16 = curdata[curoff+5]; /* CHECK */
+					}
+				} else {
 					dpd->CurrentValue.u16 = curdata[curoff+4]; /* just use last byte */
+				}
 
 				ce[i].type = PTP_CANON_EOS_CHANGES_TYPE_PROPERTY;
 				ce[i].u.propid = proptype;