diff --git a/code/modules/mob/language/language.dm b/code/modules/mob/language/language.dm
index 03ab8ea297..8c6b92c555 100644
--- a/code/modules/mob/language/language.dm
+++ b/code/modules/mob/language/language.dm
@@ -123,7 +123,7 @@
 
 	var/datum/language/new_language = all_languages[language]
 
-	if(!istype(new_language) || new_language in languages)
+	if(!istype(new_language) || (new_language in languages))
 		return 0
 
 	languages.Add(new_language)
diff --git a/code/modules/mob/living/silicon/robot/robot_modules.dm b/code/modules/mob/living/silicon/robot/robot_modules.dm
index 819fbf4561..d5a2edf3e1 100644
--- a/code/modules/mob/living/silicon/robot/robot_modules.dm
+++ b/code/modules/mob/living/silicon/robot/robot_modules.dm
@@ -34,7 +34,7 @@ var/global/list/robot_modules = list(
 	var/list/obj/item/borg/upgrade/supported_upgrades = list()
 
 	// Bookkeeping
-	var/list/added_languages = list()
+	var/list/original_languages = list()
 	var/list/added_networks = list()
 
 /obj/item/weapon/robot_module/New(var/mob/living/silicon/robot/R)
@@ -63,12 +63,14 @@ var/global/list/robot_modules = list(
 	qdel(src)
 
 /obj/item/weapon/robot_module/Destroy()
-	qdel(modules)
-	qdel(synths)
+	for(var/obj/O in modules)
+		qdel(O)
+	modules.Cut()
+	for(var/datum/matter_synth/S in synths)
+		qdel(S)
+	synths.Cut()
 	qdel(emag)
 	qdel(jetpack)
-	modules = null
-	synths = null
 	emag = null
 	jetpack = null
 	return ..()
@@ -100,14 +102,22 @@ var/global/list/robot_modules = list(
 			modules += O
 
 /obj/item/weapon/robot_module/proc/add_languages(var/mob/living/silicon/robot/R)
+	// Stores the languages as they were before receiving the module, and whether they could be synthezized.
+	for(var/datum/language/language_datum in R.languages)
+		original_languages[language_datum] = (language_datum in R.speech_synthesizer_langs)
+
 	for(var/language in languages)
-		if(R.add_language(language, languages[language]))
-			added_languages |= language
+		R.add_language(language, languages[language])
 
 /obj/item/weapon/robot_module/proc/remove_languages(var/mob/living/silicon/robot/R)
-	for(var/language in added_languages)
+	// Clear all added languages, whether or not we originally had them.
+	for(var/language in languages)
 		R.remove_language(language)
-	added_languages.Cut()
+
+	// Then add back all the original languages, and the relevant synthezising ability
+	for(var/original_language in original_languages)
+		R.add_language(original_language, original_languages[original_language])
+	original_languages.Cut()
 
 /obj/item/weapon/robot_module/proc/add_camera_networks(var/mob/living/silicon/robot/R)
 	if(R.camera && (NETWORK_ROBOTS in R.camera.network))
diff --git a/code/modules/mob/living/silicon/silicon.dm b/code/modules/mob/living/silicon/silicon.dm
index d6fc2e4aa9..5186a7f6b8 100644
--- a/code/modules/mob/living/silicon/silicon.dm
+++ b/code/modules/mob/living/silicon/silicon.dm
@@ -188,16 +188,22 @@
 	return universal_speak || (speaking in src.speech_synthesizer_langs)	//need speech synthesizer support to vocalize a language
 
 /mob/living/silicon/add_language(var/language, var/can_speak=1)
-	if (..(language) && can_speak)
-		speech_synthesizer_langs.Add(all_languages[language])
+	var/var/datum/language/added_language = all_languages[language]
+	if(!added_language)
+		return
+
+	. = ..(language)
+	if (can_speak && (added_language in languages) && !(added_language in speech_synthesizer_langs))
+		speech_synthesizer_langs += added_language
 		return 1
 
 /mob/living/silicon/remove_language(var/rem_language)
-	..(rem_language)
+	var/var/datum/language/removed_language = all_languages[rem_language]
+	if(!removed_language)
+		return
 
-	for (var/datum/language/L in speech_synthesizer_langs)
-		if (L.name == rem_language)
-			speech_synthesizer_langs -= L
+	..(rem_language)
+	speech_synthesizer_langs -= removed_language
 
 /mob/living/silicon/check_languages()
 	set name = "Check Known Languages"