diff --git a/src/material/form-field/form-field.ts b/src/material/form-field/form-field.ts
index f24ae43a742e..1b289e6f133d 100644
--- a/src/material/form-field/form-field.ts
+++ b/src/material/form-field/form-field.ts
@@ -568,10 +568,10 @@ export class MatFormField extends _MatFormFieldMixinBase
     }
 
     for (let i = 0; i < startEls.length; i++) {
-      startEls.item(i).style.width = `${startWidth}px`;
+      startEls[i].style.width = `${startWidth}px`;
     }
     for (let i = 0; i < gapEls.length; i++) {
-      gapEls.item(i).style.width = `${gapWidth}px`;
+      gapEls[i].style.width = `${gapWidth}px`;
     }
 
     this._outlineGapCalculationNeededOnStable =