diff --git a/code/modules/mob/living/living_say.dm b/code/modules/mob/living/living_say.dm
index 05906418fab..1a860763867 100644
--- a/code/modules/mob/living/living_say.dm
+++ b/code/modules/mob/living/living_say.dm
@@ -231,7 +231,14 @@ GLOBAL_LIST_INIT(message_modes_stat_limits, list(
 		message = "[randomnote] [message] [randomnote]"
 		spans |= SPAN_SINGING
 
+	#ifdef UNIT_TESTS
+	// Saves a ref() to our arglist specifically.
+	// We do this because we need to check that COMSIG_MOB_SAY is getting EXACTLY this list.
+	last_say_args_ref = REF(args)
+	#endif
+
 	// Leaving this here so that anything that handles speech this way will be able to have spans affecting it and all that.
+	// Make sure the arglist is passed exactly - don't pass a copy of it. Say signal handlers will modify some of the parameters.
 	var/sigreturn = SEND_SIGNAL(src, COMSIG_MOB_SAY, args, message_range)
 	if (sigreturn & COMPONENT_UPPERCASE_SPEECH)
 		message = uppertext(message)
diff --git a/code/modules/unit_tests/say.dm b/code/modules/unit_tests/say.dm
index 401572cf9e3..38ce20c43dc 100644
--- a/code/modules/unit_tests/say.dm
+++ b/code/modules/unit_tests/say.dm
@@ -21,3 +21,22 @@
 
 	TEST_ASSERT(!expected_mods.len,
 		"Some message mods were expected, but were not returned by get_message_mods: [json_encode(expected_mods)]. Message: [message]")
+
+/// Test to verify COMSIG_MOB_SAY is sent the exact same list as the message args, as they're operated on
+/datum/unit_test/say_signal
+
+/datum/unit_test/say_signal/Run()
+	var/mob/living/dummy = allocate(/mob/living)
+
+	RegisterSignal(dummy, COMSIG_MOB_SAY, .proc/check_say)
+	dummy.say("Make sure the say signal gets the arglist say is past, no copies!")
+
+/datum/unit_test/say_signal/proc/check_say(mob/living/source, list/say_args)
+	SIGNAL_HANDLER
+
+	TEST_ASSERT_EQUAL(REF(say_args), source.last_say_args_ref, "Say signal didn't get the argslist of say as a reference. \
+		This is required for the signal to function in most places - do not create a new instance of a list when passing it in to the signal.")
+
+// For the above test to track the last use of say's message args.
+/mob/living
+	var/last_say_args_ref