diff --git a/tools/Android.mk b/tools/Android.mk
index 92603f5..fe29e2b 100644
--- a/tools/Android.mk
+++ b/tools/Android.mk
@@ -17,7 +17,7 @@
 LOCAL_PATH := $(call my-dir)
 
 # If we're building only unbundled apps, this is the only tool we need.
-ifneq ($(TARGET_BUILD_APPS),)
+ifneq (,$(TARGET_BUILD_APPS)$(filter true,$(TARGET_BUILD_PDK)))
 include $(LOCAL_PATH)/signapk/Android.mk
 else
 include $(call first-makefiles-under,$(LOCAL_PATH))