diff --git a/code/__byond_version_compat.dm b/code/__byond_version_compat.dm
index 43307b5ce1..8525a8cc23 100644
--- a/code/__byond_version_compat.dm
+++ b/code/__byond_version_compat.dm
@@ -15,6 +15,14 @@
 #error Please consider downgrading to 514.1575 or lower.
 #endif
 
+#define MAX_COMPILER_VERSION 515
+#if (DM_VERSION > MAX_COMPILER_VERSION) && !defined(SPACEMAN_DMM)
+#error Your version of BYOND is currently unsupported and this has been left as a notice
+#error If this was unintentional, please revert to 515.
+#error Otherwise modify the MAX_COMPILER_VERSION or comment this entire section
+#error And get going with making this codebase compatible.
+#endif
+
 // Keep savefile compatibilty at minimum supported level
 #if DM_VERSION >= 515
 /savefile/byond_version = MIN_COMPILER_VERSION
diff --git a/code/modules/client/client_procs.dm b/code/modules/client/client_procs.dm
index 96f59bc048..4d1eb9ba46 100644
--- a/code/modules/client/client_procs.dm
+++ b/code/modules/client/client_procs.dm
@@ -375,6 +375,16 @@ GLOBAL_LIST_INIT(blacklisted_builds, list(
 				qdel(src)
 				return
 
+	if(byond_version > 515)
+		if(!connecting_admin)
+			log_access("Failed login: [key] - [byond_version] is unsupported.")
+			to_chat(src, span_userdanger("Your version of byond is unsupported."))
+			to_chat(src, span_danger("Byond build [byond_build] ([byond_version].[byond_build]) has been disallowed from joining the game due to simply being unable to interact with way too many game elements, rendering it unplayable."))
+			to_chat(src, span_danger("Until we are capable of supporting webview, playing will be restricted to versions below 516, you can go to <a href=\"https://secure.byond.com/download/build\">BYOND's website</a> to download other versions."))
+			qdel(src)
+			return
+		to_chat(src, "As an admin, you are being allowed through, be warned that TGUI is incapable of loading in this version and you might have major issues.")
+
 	// Initialize tgui panel
 	src << browse(file('html/statbrowser.html'), "window=statbrowser")
 	addtimer(CALLBACK(src, PROC_REF(check_panel_loaded)), 30 SECONDS)