diff --git a/inc/config.php b/inc/config.php
index 766fe912..d5cfc6d0 100644
--- a/inc/config.php
+++ b/inc/config.php
@@ -236,6 +236,9 @@
     // To prevent bump atacks; returns the thread to last position after the last post is deleted.
     $config['anti_bump_flood'] = false;
 
+    // Reject thread creation from IPs without any prior post history.
+    $config['op_require_history'] = false;
+
     /*
      * Introduction to Tinyboard's spam filter:
      *
@@ -1216,6 +1219,7 @@
     // Error messages
     $config['error']['bot']         = _('You look like a bot.');
     $config['error']['referer']     = _('Your browser sent an invalid or no HTTP referer.');
+    $config['error']['opnohistory'] = _('You must post at least once before creating thread.');
     $config['error']['toolong']     = _('The %s field was too long.');
     $config['error']['toolong_body']    = _('The body was too long.');
     $config['error']['tooshort_body']   = _('The body was too short or empty.');
diff --git a/inc/functions.php b/inc/functions.php
index 2328c1b7..83333af0 100644
--- a/inc/functions.php
+++ b/inc/functions.php
@@ -918,6 +918,41 @@ function checkBan($board = false) {
 	}
 }
 
+/**
+ * Checks if the given IP has any previous posts.
+ *
+ * @param string $ip The IP to check.
+ * @return bool True if the ip has already sent at least one post, false otherwise.
+ */
+function has_any_history(string $ip): bool {
+	global $config;
+
+	if ($config['cache']['enabled']) {
+		$ret = cache::get("post_history_$ip");
+		if ($ret !== false) {
+			return $ret !== 0x0;
+		}
+	}
+
+	foreach (listBoards(true) as $board_uri) {
+		$query = prepare(sprintf('SELECT `id` FROM ``posts_%s`` WHERE `ip` = :ip LIMIT 1', $board_uri));
+		$query->bindValue(':ip', $ip);
+		$query->execute() or error(db_error());
+
+		if ($query->fetchColumn() !== false) {
+			// Found a post.
+			if ($config['cache']['enabled']) {
+				cache::set("post_history_$ip", 0xA);
+			}
+			return true;
+		}
+	}
+	if ($config['cache']['enabled']) {
+		cache::set("post_history_$ip", 0x0);
+	}
+	return false;
+}
+
 function threadLocked($id) {
 	global $board;
 
diff --git a/post.php b/post.php
index 997201b0..daaffcf6 100644
--- a/post.php
+++ b/post.php
@@ -932,6 +932,13 @@ function handle_post()
         // Check if banned
         checkBan($board['uri']);
 
+        if ($config['op_require_history'] && $post['op']) {
+            $has_any = has_any_history($_SERVER['REMOTE_ADDR']);
+            if (!$has_any) {
+                error($config['error']['opnohistory']);
+            }
+        }
+
         if ($post['mod'] = isset($_POST['mod']) && $_POST['mod']) {
             check_login(false);
             if (!$mod) {