diff --git a/lib/database/accounts.js b/lib/database/accounts.js
index 51f0a101..f270e5d7 100644
--- a/lib/database/accounts.js
+++ b/lib/database/accounts.js
@@ -7,6 +7,15 @@ var Logger = require("../logger");
 var registrationLock = {};
 var blackHole = function () { };
 
+/**
+ * Replaces look-alike characters with "_" (single character wildcard) for
+ * use in LIKE queries.  This prevents guests from taking names that look
+ * visually identical to existing names in certain fonts.
+ */
+function wildcardSimilarChars(name) {
+    return name.replace(/[Il1oO0]/g, "_");
+}
+
 module.exports = {
     init: function () {
     },
@@ -15,7 +24,7 @@ module.exports = {
      * Check if a username is taken
      */
     isUsernameTaken: function (name, callback) {
-        db.query("SELECT name FROM `users` WHERE name=?", [name],
+        db.query("SELECT name FROM `users` WHERE name LIKE ?", [wildcardSimilarChars(name)],
         function (err, rows) {
             if (err) {
                 callback(err, true);