diff --git a/src/data/backwardsCompatibility/updateSlaveObject.js b/src/data/backwardsCompatibility/updateSlaveObject.js
index ab1f9df1a1834a655d4f10c6386964978313e166..7567a248fe8e0bf378e875e673bb34761204e9b9 100644
--- a/src/data/backwardsCompatibility/updateSlaveObject.js
+++ b/src/data/backwardsCompatibility/updateSlaveObject.js
@@ -62,7 +62,7 @@ App.Update.Slave = function(slave, genepool = false) {
 		}
 	}
 	if (slave.genetics !== undefined) { delete slave.genetics; }
-	if (slave.geneMods === undefined) { slave.geneMods = {NCS: 0, rapidCellGrowth: 0, immortality: 0}; }
+	slave.geneMods = Object.assign({NCS: 0, rapidCellGrowth: 0, immortality: 0}, slave.geneMods);
 	if (slave.inducedNCS !== undefined) {
 		slave.geneMods.NCS = slave.inducedNCS;
 		delete slave.inducedNCS;