diff --git a/wowchemy/layouts/_default/baseof.html b/wowchemy/layouts/_default/baseof.html
index 5e0225e6..6328e0d0 100644
--- a/wowchemy/layouts/_default/baseof.html
+++ b/wowchemy/layouts/_default/baseof.html
@@ -22,9 +22,9 @@
   {{- end -}}
   {{ $js_bundle := slice $js_bundle_head $js_bundle | resources.Concat "js/wowchemy-init.min.js" }}
   {{- if hugo.IsProduction -}}
-    {{- $js_bundle = $js_bundle | js.Build (dict "format" "esm") | fingerprint "md5" -}}
+    {{- $js_bundle = $js_bundle | js.Build (dict "format" "iife") | fingerprint "md5" -}}
   {{- else -}}
-    {{- $js_bundle = $js_bundle | js.Build (dict "format" "esm" "sourceMap" "inline") -}}
+    {{- $js_bundle = $js_bundle | js.Build (dict "format" "iife" "sourceMap" "inline") -}}
   {{- end -}}
   <script src="{{ $js_bundle.RelPermalink }}"></script>
 
diff --git a/wowchemy/layouts/partials/site_js.html b/wowchemy/layouts/partials/site_js.html
index 14eead97..98982941 100644
--- a/wowchemy/layouts/partials/site_js.html
+++ b/wowchemy/layouts/partials/site_js.html
@@ -142,9 +142,9 @@
     {{- end -}}
     {{ $js_bundle := slice $js_bundle_head $js_bundle | resources.Concat (printf "%s/js/wowchemy.min.js" .Lang) }}
     {{- if hugo.IsProduction -}}
-      {{- $js_bundle = $js_bundle | js.Build (dict "format" "esm") | fingerprint "md5" -}}
+      {{- $js_bundle = $js_bundle | js.Build (dict "format" "iife") | fingerprint "md5" -}}
     {{- else -}}
-      {{- $js_bundle = $js_bundle | js.Build (dict "format" "esm" "sourceMap" "inline") -}}
+      {{- $js_bundle = $js_bundle | js.Build (dict "format" "iife" "sourceMap" "inline") -}}
     {{- end -}}
     <script src="{{ $js_bundle.RelPermalink }}"></script>