diff --git a/types/chroma-js/index.d.ts b/types/chroma-js/index.d.ts
index 8fdae85b4d..faeba01bb1 100644
--- a/types/chroma-js/index.d.ts
+++ b/types/chroma-js/index.d.ts
@@ -322,6 +322,7 @@ declare namespace chroma {
          */
         out(format: null): Scale;
         out<K extends keyof ColorSpaces>(format: K): Scale<ColorSpaces[K]>;
+        out(format: 'hex'): Scale<string>;
     }
 
     interface Cubehelix {