diff --git a/lib/Core/replaceUnderscores.ts b/lib/Core/replaceUnderscores.ts
index 693deb2388..c8772e389f 100644
--- a/lib/Core/replaceUnderscores.ts
+++ b/lib/Core/replaceUnderscores.ts
@@ -3,8 +3,10 @@
  * @param string The string to replace. If the argument is not a string, does nothing.
  * @return The argument with all underscores replaced with spaces. If the argument is not a string, returns the argument unchanged.
  */
-function replaceUnderscores(str: string | undefined): typeof str {
-  return typeof str === "string" ? str.replace(/_/g, " ") : str;
+function replaceUnderscores(str: any): typeof str {
+  return typeof str === "string" || str instanceof String
+    ? str.replace(/_/g, " ")
+    : str;
 }
 
 export default replaceUnderscores;