--- a/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.options.processor/src/org/graalvm/compiler/options/processor/OptionProcessor.java	Tue Mar 12 12:12:01 2019 -0700
+++ b/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.options.processor/src/org/graalvm/compiler/options/processor/OptionProcessor.java	Tue Mar 12 19:17:42 2019 +0100
@@ -174,7 +174,7 @@
             }
             enclosing = enclosing.getEnclosingElement();
         }
-        if (enclosingPackage == null) {
+        if (enclosingPackage == null || enclosingPackage.isUnnamed()) {
             processingEnv.getMessager().printMessage(Kind.ERROR, "Option field cannot be declared in the unnamed package", element);
             return;
         }