diff --git a/layouts/partials/schema-jsonld.html b/layouts/partials/schema-jsonld.html
index 8823f61..ec1ebad 100644
--- a/layouts/partials/schema-jsonld.html
+++ b/layouts/partials/schema-jsonld.html
@@ -19,7 +19,12 @@
       "sameAs" $sameAs
   -}}
   {{- with $brand.contactEmail -}}{{- if not (in . ".example") -}}{{- $data = merge $data (dict "email" .) -}}{{- end -}}{{- end -}}
-  {{- with $brand.foundedYear -}}{{- if gt (int .) 0 -}}{{- $data = merge $data (dict "foundingDate" (printf "%d" (int .))) -}}{{- end -}}{{- end -}}
+  {{- with $brand.foundedYear -}}
+    {{- $year := printf "%v" . -}}
+    {{- if gt (len (findRE `^[0-9]{4}$` $year)) 0 -}}
+      {{- $data = merge $data (dict "foundingDate" $year) -}}
+    {{- end -}}
+  {{- end -}}
   <script type="application/ld+json">{{ $data | jsonify | safeJS }}</script>
 
 {{- end -}}