diff --git a/core/dex_preopt.mk b/core/dex_preopt.mk
index 3a43336..457f1d4 100644
--- a/core/dex_preopt.mk
+++ b/core/dex_preopt.mk
@@ -19,6 +19,18 @@
 # The default value for LOCAL_DEX_PREOPT
 DEX_PREOPT_DEFAULT ?= true
 
+# The default values for pre-opting: always preopt PIC.
+# Conditional to building on linux, as dex2oat currently does not work on darwin.
+ifeq ($(HOST_OS),linux)
+  WITH_DEXPREOPT_PIC ?= true
+  WITH_DEXPREOPT ?= true
+# For an eng build only pre-opt the boot image. This gives reasonable performance and still
+# allows a simple workflow: building in frameworks/base and syncing.
+  ifeq (eng,$(TARGET_BUILD_VARIANT))
+    WITH_DEXPREOPT_BOOT_IMG_ONLY ?= true
+  endif
+endif
+
 GLOBAL_DEXPREOPT_FLAGS :=
 ifeq ($(WITH_DEXPREOPT_PIC),true)
 # Compile boot.oat as position-independent code if WITH_DEXPREOPT_PIC=true