diff --git a/lib/hacks/grid-utils.js b/lib/hacks/grid-utils.js
index a552ec3d6..7f6403ad6 100644
--- a/lib/hacks/grid-utils.js
+++ b/lib/hacks/grid-utils.js
@@ -511,7 +511,15 @@ function insertAreas (css, isDisabled) {
 
       // if we can't find the area name, update lastRule and continue
       if (!area) {
-        let lastRuleIndex = css.index(rulesToInsert[lastArea].lastRule)
+        let lastRule = rulesToInsert[lastArea].lastRule
+        let lastRuleIndex
+        if (lastRule) {
+          lastRuleIndex = css.index(lastRule)
+        } else {
+          /* istanbul ignore next */
+          lastRuleIndex = -1
+        }
+
         if (gridAreaRuleIndex > lastRuleIndex) {
           rulesToInsert[lastArea].lastRule = gridAreaMedia || gridAreaRule
         }