diff --git a/quartz/plugins/transformers/ofm.ts b/quartz/plugins/transformers/ofm.ts
index 8c405bf..d58eaf6 100644
--- a/quartz/plugins/transformers/ofm.ts
+++ b/quartz/plugins/transformers/ofm.ts
@@ -290,8 +290,9 @@ export const ObsidianFlavoredMarkdown: QuartzTransformerPlugin<Partial<Options>
                 }
 
                 tag = slugTag(tag)
-                if (file.data.frontmatter?.tags?.includes(tag)) {
-                  file.data.frontmatter.tags.push(tag)
+                if (file.data.frontmatter) {
+                  const noteTags = file.data.frontmatter.tags ?? []
+                  file.data.frontmatter.tags = [...new Set([...noteTags, tag])]
                 }
 
                 return {