diff --git a/core/config.mk b/core/config.mk
index 5ef9211..f971c51 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -494,7 +494,9 @@
 DISABLE_PREOPT :=
 ifneq (,$(TARGET_BUILD_APPS)$(TARGET_BUILD_UNBUNDLED_IMAGE))
   DISABLE_PREOPT := true
-  ifndef UNBUNDLED_BUILD_SDKS_FROM_SOURCE
+endif
+ifeq (true,$(TARGET_BUILD_UNBUNDLED))
+  ifneq (true,$(UNBUNDLED_BUILD_SDKS_FROM_SOURCE))
     TARGET_BUILD_USE_PREBUILT_SDKS := true
   endif
 endif