diff --git a/packages/core/src/utils/variantGroup.ts b/packages/core/src/utils/variantGroup.ts
index 80da1917d3..7b0558098a 100644
--- a/packages/core/src/utils/variantGroup.ts
+++ b/packages/core/src/utils/variantGroup.ts
@@ -90,7 +90,7 @@ export function expandVariantGroup(str: string | MagicString, separators = ['-',
   }
   else {
     return str.length()
-      ? str.overwrite(0, str.length(), expanded)
+      ? str.overwrite(0, str.original.length, expanded)
       : str
   }
 }