diff --git a/code/modules/mob/living/carbon/monkey/diona.dm b/code/modules/mob/living/carbon/monkey/diona.dm
index 741b5762b26..8e6f10df4b4 100644
--- a/code/modules/mob/living/carbon/monkey/diona.dm
+++ b/code/modules/mob/living/carbon/monkey/diona.dm
@@ -209,7 +209,7 @@
 	src.visible_message("\red [src] flicks out a feeler and neatly steals a sample of [M]'s blood.","\red You flick out a feeler and neatly steal a sample of [M]'s blood.")
 	donors += M.real_name
 	for(var/datum/language/L in M.languages)
-		languages += L
+		languages |= L
 
 	spawn(25)
 		update_progression()