diff --git a/packages/material-ui/src/styles/responsiveFontSizes.d.ts b/packages/material-ui/src/styles/responsiveFontSizes.d.ts
index b1b134bff228f9..79051a0508ddef 100644
--- a/packages/material-ui/src/styles/responsiveFontSizes.d.ts
+++ b/packages/material-ui/src/styles/responsiveFontSizes.d.ts
@@ -6,7 +6,7 @@ export interface ResponsiveFontSizesOptions {
   breakpoints?: Breakpoint[];
   disableAlign?: boolean;
   factor?: number;
-  variants?: ThemeStyle;
+  variants?: ThemeStyle[];
 }
 
 export default function responsiveFontSizes(