diff --git a/diode/webclient/sdfg_utils.js b/diode/webclient/sdfg_utils.js
index a968950c26..129184f0aa 100644
--- a/diode/webclient/sdfg_utils.js
+++ b/diode/webclient/sdfg_utils.js
@@ -72,13 +72,13 @@ function sdfg_range_elem_to_string(range, settings=null) {
         } else {
             let endp1 = sdfg_property_to_string(range.end, settings) + ' + 1';
             // Try to simplify using math.js
-            var mathjs = null;
+            var mathjs = undefined;
             try {
                 mathjs = window.math;
             } catch(e) {
                 try { mathjs = math; } catch(e) {}
             }
-            if (mathjs !== null)
+            if (mathjs !== undefined)
                 endp1 = mathjs.simplify(endp1).toString();
 
             preview += sdfg_property_to_string(range.start, settings) + ':' +