diff --git a/index.html b/index.html
index b37b71a..6ea837d 100644
--- a/index.html
+++ b/index.html
@@ -147,8 +147,11 @@
                 playersSearch: true,
 
                 // Use more compact pre-2.0 player marker style
-                compactPlayerMarkers: true,
-            }
+                compactPlayerMarkers: false,
+            },
+
+            // Config version. Do not modify.
+            version: 1
         };
     </script>
 
diff --git a/src/index.d.ts b/src/index.d.ts
index fc53793..7e47afa 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -67,6 +67,7 @@ interface LiveAtlasGlobalConfig {
 	servers: Map<string, LiveAtlasServerDefinition>;
 	messages: LiveAtlasGlobalMessageConfig;
 	ui: LiveAtlasUIConfig;
+	version?: number;
 }
 
 interface LiveAtlasServerDefinition {
diff --git a/src/util/config.ts b/src/util/config.ts
index dbd880b..cd2f364 100644
--- a/src/util/config.ts
+++ b/src/util/config.ts
@@ -17,6 +17,9 @@
 import {LiveAtlasGlobalConfig, LiveAtlasServerDefinition} from "@/index";
 import ConfigurationError from "@/errors/ConfigurationError";
 import {DynmapUrlConfig} from "@/dynmap";
+import {useStore} from "@/store";
+
+const expectedConfigVersion = 1;
 
 const validateLiveAtlasConfiguration = (config: any): Map<string, LiveAtlasServerDefinition> => {
 	const check = '\nCheck your server configuration in index.html is correct.',
@@ -125,6 +128,10 @@ export const getServerDefinitions = (config: LiveAtlasGlobalConfig): Map<string,
 		throw new ConfigurationError(`No configuration found.\nCheck for any syntax errors in your configuration in index.html. Your browser console may contain additional information.`);
 	}
 
+	if (config.version !== expectedConfigVersion) {
+		throw new ConfigurationError(`Configuration version mismatch.\nUse a fresh copy of index.html from your current LiveAtlas version (${useStore().state.version}) and reapply any customisations.`);
+	}
+
 	if (typeof config.servers !== 'undefined') {
 		return validateLiveAtlasConfiguration(config.servers);
 	}