diff --git a/options.ts b/options.ts
index 04b00b2..6e4eb28 100644
--- a/options.ts
+++ b/options.ts
@@ -69,7 +69,7 @@ const Options = z
     }),
     thumbnail: z
       .function()
-      .args(z.object({ src: z.string().min(1), width: z.number(), height: z.number() }))
+      .args(z.object({ src: z.string().min(1), width: z.number().or(z.string()), height: z.number().or(z.string()) }))
       .returns(z.string()),
   })
   .transform((opts) => {
diff --git a/src/helpers/images.ts b/src/helpers/images.ts
index 4c88850..5d63bae 100644
--- a/src/helpers/images.ts
+++ b/src/helpers/images.ts
@@ -11,11 +11,11 @@ export interface Image {
   /**
    * image width
    */
-  width: number;
+  width: number | string;
   /**
    * image height
    */
-  height: number;
+  height: number | string;
   /**
    * blurDataURL of the image
    */