--- a/src/name/blackcap/exifwasher/Misc.kt	Sun Apr 12 11:46:12 2020 -0700
+++ b/src/name/blackcap/exifwasher/Misc.kt	Sun Apr 12 18:46:57 2020 -0700
@@ -23,7 +23,7 @@
  * needed in Swing, because some vars inevitably need to be declared at
  * outer levels but initialized in the Swing event dispatch thread.
  */
-class SetOnceImpl<T>: ReadWriteProperty<Any?,T> {
+class SetOnceImpl<T: Any>: ReadWriteProperty<Any?,T> {
     private var setOnceValue: T? = null
 
     override operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
@@ -43,7 +43,7 @@
     }
 }
 
-fun <T> setOnce(): SetOnceImpl<T> = SetOnceImpl<T>()
+fun <T: Any> setOnce(): SetOnceImpl<T> = SetOnceImpl<T>()
 
 /**
  * Run something in the Swing thread, asynchronously.