diff --git a/printThis.d.ts b/printThis.d.ts
index 277d33e..244f86f 100644
--- a/printThis.d.ts
+++ b/printThis.d.ts
@@ -69,7 +69,7 @@ interface IPrintThisOptions {
      * preserve the BASE tag or accept a string for the URL
      * default value: false
      */
-    base?: boolean,
+    base?: boolean | string,
 
     /**
      * preserve input/form values
@@ -115,4 +115,4 @@ interface IPrintThisOptions {
      * function called before iframe is removed
      */
     afterPrint?: Function
-}
\ No newline at end of file
+}