diff --git a/core/config.mk b/core/config.mk
index 49b9329..241ac8d 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -630,9 +630,11 @@
 USE_OPENJDK9 := true
 
 ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),)
-TARGET_OPENJDK9 :=
+TARGET_OPENJDK9 := true
 else ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),true)
 TARGET_OPENJDK9 := true
+else ifeq ($(EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9),false)
+TARGET_OPENJDK9 :=
 endif
 
 # Path to tools.jar