diff --git a/src/main/java/de/pdinklag/mcstats/Updater.java b/src/main/java/de/pdinklag/mcstats/Updater.java
index a6e7ab9..3adc8d5 100644
--- a/src/main/java/de/pdinklag/mcstats/Updater.java
+++ b/src/main/java/de/pdinklag/mcstats/Updater.java
@@ -1,5 +1,6 @@
 package de.pdinklag.mcstats;
 
+import java.io.BufferedReader;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -17,6 +18,7 @@
 import org.json.JSONArray;
 import org.json.JSONObject;
 
+import de.pdinklag.mcstats.Log.Category;
 import de.pdinklag.mcstats.util.ClientUtils;
 import de.pdinklag.mcstats.util.JSONUtils;
 import de.pdinklag.mcstats.util.MinecraftServerUtils;
@@ -42,6 +44,9 @@ public abstract class Updater {
     private static final String DATABASE_SUMMARY = "summary.json";
     private static final String DATABASE_LEGACY_SUMMARY = "summary.json.gz";
 
+    private static final String CLIENT_INDEX_HTML = "index.html";
+    private static final String CLIENT_VERSION_PREFIX = "<!-- MinecraftStats Client v";
+
     private static final String EVENT_INITIAL_RANKING_FIELD = "initialRanking";
     private static final String EVENT_RANKING_FIELD = "ranking";
 
@@ -323,7 +328,7 @@ public Updater(Config config) {
      */
     protected abstract String getVersion();
 
-    public void run(ConsoleWriter consoleWriter) {
+    public boolean run(ConsoleWriter consoleWriter) {
         // initialize log
         final Log log;
         try {
@@ -331,7 +336,46 @@ public void run(ConsoleWriter consoleWriter) {
             Log.setCurrent(log);
         } catch (IOException ex) {
             consoleWriter.writeError("failed to initialize logging", ex);
-            return;
+            return false;
+        }
+
+        // before doing anything meaningful, check that the client is up to date to
+        // avoid things breaking
+        final Path documentRoot = config.getDocumentRoot();
+        final Path indexHtmlPath = documentRoot.resolve(CLIENT_INDEX_HTML);
+        if (Files.isRegularFile(indexHtmlPath)) {
+            try {
+                final Version clientVersion;
+                final BufferedReader r = Files.newBufferedReader(indexHtmlPath);
+                String firstLine = r.readLine();
+                if (firstLine.startsWith(CLIENT_VERSION_PREFIX)) {
+                    final int begin = CLIENT_VERSION_PREFIX.length();
+                    final int end = firstLine.indexOf(' ', begin);
+
+                    clientVersion = Version.parse(firstLine.substring(begin, end));
+
+                    log.writeLine(Category.SILENT_PROGRESS,
+                            "parsed client version " + clientVersion.toString() + " from " + CLIENT_INDEX_HTML);
+                } else {
+                    log.writeLine(Category.SILENT_PROGRESS,
+                            "no version information was found in " + CLIENT_INDEX_HTML + ", assuming outdated client");
+                    clientVersion = new Version(2, 0, 0);
+                }
+
+                if (clientVersion.compareTo(MIN_CLIENT_VERSION) < 0) {
+                    log.writeLine(Log.Category.PROGRESS,
+                            "Your MinecraftStats web files (version " + clientVersion
+                                    + ") are outdated -- at least version "
+                                    + MIN_CLIENT_VERSION + " is required.");
+                    return false;
+                }
+            } catch (Exception ex) {
+                log.writeError("failed to read verson from " + indexHtmlPath.toString(), ex);
+                return false;
+            }
+        } else {
+            log.writeLine(Log.Category.SILENT_PROGRESS, "bypassing client version check because " + CLIENT_INDEX_HTML
+                    + " was not found in the document root");
         }
 
         // discover and instantiate stats
@@ -791,5 +835,8 @@ public void run(ConsoleWriter consoleWriter) {
             consoleWriter.writeError("failed to close log", ex);
         }
         Log.setCurrent(null);
+
+        // done
+        return true;
     }
 }
diff --git a/src/main/java/de/pdinklag/mcstats/bukkit/BukkitUpdater.java b/src/main/java/de/pdinklag/mcstats/bukkit/BukkitUpdater.java
index a6c90af..66c683a 100644
--- a/src/main/java/de/pdinklag/mcstats/bukkit/BukkitUpdater.java
+++ b/src/main/java/de/pdinklag/mcstats/bukkit/BukkitUpdater.java
@@ -35,13 +35,15 @@ protected String getVersion() {
     }
 
     @Override
-    public void run(ConsoleWriter consoleWriter) {
-        super.run(consoleWriter);
-
+    public boolean run(ConsoleWriter consoleWriter) {
+        final boolean success = super.run(consoleWriter);
         if (firstUpdate) {
-            plugin.getLogger().info("Web frontend updated. This will now happen every "
-                    + config.getUpdateInterval() + " minute(s) without any further logging to the console.");
+            if (success) {
+                plugin.getLogger().info("Web frontend updated. This will now happen every "
+                        + config.getUpdateInterval() + " minute(s) without any further logging to the console.");
+            }
             firstUpdate = false;
         }
+        return success;
     }
 }
diff --git a/src/main/java/de/pdinklag/mcstats/cli/CLIUpdater.java b/src/main/java/de/pdinklag/mcstats/cli/CLIUpdater.java
index decd5bb..f947b4a 100644
--- a/src/main/java/de/pdinklag/mcstats/cli/CLIUpdater.java
+++ b/src/main/java/de/pdinklag/mcstats/cli/CLIUpdater.java
@@ -58,8 +58,12 @@ protected String getVersion() {
     }
 
     @Override
-    public void run(ConsoleWriter consoleWriter) {
-        super.run(consoleWriter);
-        Log.getCurrent().writeLine(Log.Category.PROGRESS, "update finished");
+    public boolean run(ConsoleWriter consoleWriter) {
+        if (super.run(consoleWriter)) {
+            Log.getCurrent().writeLine(Log.Category.PROGRESS, "update finished");
+            return true;
+        } else {
+            return false;
+        }
     }
 }
diff --git a/www/index.html b/www/index.html
index 9dec413..b223693 100644
--- a/www/index.html
+++ b/www/index.html
@@ -1,3 +1,4 @@
+<!-- MinecraftStats Client v3.4.0 - DO NOT EDIT OR (RE)MOVE THIS LINE, IT IS REQUIRED BY THE UPDATER -->
 <!doctype html>
 <html lang="en">
     <head>