diff --git a/code/modules/virus2/disease2.dm b/code/modules/virus2/disease2.dm
index 523c6001baf..81705cbe4af 100644
--- a/code/modules/virus2/disease2.dm
+++ b/code/modules/virus2/disease2.dm
@@ -83,6 +83,9 @@
 /datum/disease2/disease/proc/majormutate()
 	var/datum/disease2/effectholder/holder = pick(effects)
 	holder.majormutate()
+	if (prob(5))
+		antigen = text2num(pick(ANTIGENS))
+		antigen |= text2num(pick(ANTIGENS))
 
 /datum/disease2/disease/proc/getcopy()
 	var/datum/disease2/disease/disease = new /datum/disease2/disease