diff --git a/layouts/partials/footer.html b/layouts/partials/footer.html
index 74ba9d0f4e..19d4172e8e 100644
--- a/layouts/partials/footer.html
+++ b/layouts/partials/footer.html
@@ -18,6 +18,10 @@
   {{- end }}
     <script>
       function useMathJax( config ){
+        if( !Object.assign ){
+          // We don't support MathJax for IE11 anyways, so bail out early
+          return;
+        }
         window.MathJax = Object.assign( window.MathJax || {}, {
           loader: {
             load: ['[tex]/mhchem']
diff --git a/static/js/theme.js b/static/js/theme.js
index 2534fa7bf5..fd629deb60 100644
--- a/static/js/theme.js
+++ b/static/js/theme.js
@@ -896,6 +896,10 @@ jQuery.fn.highlight = function(words, options) {
 };
 
 function useMermaid( config ){
+    if( !Object.assign ){
+        // We don't support Mermaid for IE11 anyways, so bail out early
+        return;
+    }
     if (typeof mermaid != 'undefined' && typeof mermaid.mermaidAPI != 'undefined') {
         mermaid.initialize( Object.assign( { "securityLevel": "antiscript", "startOnLoad": false     }, config ) );
         if( config.theme && variants ){
@@ -904,8 +908,8 @@ function useMermaid( config ){
         }
     }
 }
-if( themeUseMermaid ){
-    useMermaid( themeUseMermaid );
+if( window.themeUseMermaid ){
+    useMermaid( window.themeUseMermaid );
 }
 
 function useSwagger( config ){
@@ -914,6 +918,6 @@ function useSwagger( config ){
         write_style.setProperty( '--CONFIG-SWAGGER-theme', config.theme );
     }
 }
-if( themeUseSwagger ){
-    useSwagger( themeUseSwagger );
+if( window.themeUseSwagger ){
+    useSwagger( window.themeUseSwagger );
 }