diff --git a/index.php b/index.php
index 4f0fb61..91e4f94 100644
--- a/index.php
+++ b/index.php
@@ -66,12 +66,23 @@ session_start();
 
 			if (str_starts_with($_POST["sub"], "Registrovat"))
 			{
+				$failed = false;
+
 				$database -> query("INSERT INTO user_info (nickname) VALUES (\"" . $safe_uname . "\")");
 				$key_id_out = $database -> query("SELECT id FROM user_info WHERE nickname=\"" . $safe_uname . "\"");
 
-				$database -> query("INSERT INTO user (username, password, user_info) VALUES (\"" . $safe_uname . "\",\"" . $hashed_pass ."\", " . ($key_id_out -> fetch_assoc())["id"] . ")");
+				try
+				{
+					$database -> query("INSERT INTO user (username, password, user_info) VALUES (\"" . $safe_uname . "\",\"" . $hashed_pass ."\", " . ($key_id_out -> fetch_assoc())["id"] . ")");
+				} catch (mysqli_sql_exception $e)
+				{
+					$failed = true;
+					$database -> query("DELETE FROM user_info WHERE nickname=\"" . $safe_uname . "\"");
 
-				login($safe_uname);
+					echo "<script>alert(\"Při registraci došlo k chybě.\\n\\nZkontrolujte, zda-li Vaše uživatelské jmeno neobsahuje speciální znaky a zkuste to znovu.\");</script>";
+				}
+
+				if (!$failed) login($safe_uname);
 			} else
 			{
 				$res = $database -> query("SELECT username, password FROM user WHERE BINARY username=\"" . $safe_uname . "\" AND BINARY password = \"" . $hashed_pass . "\"");