diff --git a/lib/notion/getPageProperties.js b/lib/notion/getPageProperties.js
index f2690821829..6342818474a 100644
--- a/lib/notion/getPageProperties.js
+++ b/lib/notion/getPageProperties.js
@@ -244,7 +244,7 @@ function generateCustomizeSlug(postProperties, NOTION_CONFIG) {
   }
   let fullPrefix = ''
   let allSlugPatterns = NOTION_CONFIG?.POST_URL_PREFIX
-  if (allSlugPatterns === undefined) {
+  if (allSlugPatterns === undefined || allSlugPatterns === null) {
     allSlugPatterns = siteConfig(
       'POST_URL_PREFIX',
       BLOG.POST_URL_PREFIX,