diff --git a/dtbo/append_certs.py b/dtbo/append_certs.py
index 1256307..1ea035d 100755
--- a/dtbo/append_certs.py
+++ b/dtbo/append_certs.py
@@ -1,16 +1,12 @@
 #!/usr/bin/env python
 
-import sys
 import argparse
-import os
-from shutil import copyfile
+from os import stat
 
 
 def padding_file(input_file, align_num):
-    """
-    Fill 0 to make input_file's size a multiple of align_num.
-    """
-    filesize = os.stat(input_file).st_size
+    """Fill 0 to make input_file's size a multiple of align_num."""
+    filesize = stat(input_file).st_size
     file1 = open(input_file, 'ab+')
     padding = filesize % align_num
     if padding != 0:
@@ -19,28 +15,28 @@ def padding_file(input_file, align_num):
             file1.write("\x00")
     file1.close()
 
-def append_file(img_file, cert_file):
-    """
-    Append provided cert_file to the end of target img_file.
-    """
-    padding_file(img_file, 16)
+
+def append_file(img_file, cert_file, alignment):
+    """Append provided cert_file to the end of target img_file."""
+    padding_file(img_file, alignment)
     file1 = open(img_file, 'ab+')
     file2 = open(cert_file, 'rb')
     file1.write(file2.read())
     file1.close()
     file2.close()
 
+
 def main():
     parser = argparse.ArgumentParser(description='Sign an image with provided der certs')
-    parser.add_argument('--image', type=str, help='Target image')
+    parser.add_argument('--alignment', type=int, help='Alignment for calculating padding')
     parser.add_argument('--cert1', type=str, help='Certificate - cert1.der')
     parser.add_argument('--cert2', type=str, help='Certificate - cert2.der')
-    parser.add_argument('--output', type=str, help='Output image')
+    parser.add_argument('--dtbo', type=str, help='Path to the DTBO img')
     args = parser.parse_args()
 
-    copyfile(args.image, args.output)
-    append_file(args.output, args.cert1)
-    append_file(args.output, args.cert2)
+    append_file(args.dtbo, args.cert1, args.alignment)
+    append_file(args.dtbo, args.cert2, args.alignment)
+
 
 if __name__ == '__main__':
     main()
diff --git a/dtbo/dtbo.mk b/dtbo/dtbo.mk
index 4cf59d4..4b48ca3 100644
--- a/dtbo/dtbo.mk
+++ b/dtbo/dtbo.mk
@@ -1,24 +1,12 @@
-BOARD_PREBUILT_DTBOIMAGE := $(PRODUCT_OUT)/dtbo-pre.img
-BOARD_KERNEL_DTBO_CFG := dtboimg.cfg
-MKDTBOIMG := system/libufdt/utils/src/mkdtboimg.py
 APPEND_CERTS := $(DEVICE_PATH)/dtbo/append_certs.py
-
-# BUG: mkdtboimg.py doesn't support absolute paths yet. Fix this later.
-define build-dtboimage-target-from-cfg
-    $(call pretty,"Target dtbo image from cfg: $(BOARD_PREBUILT_DTBOIMAGE)")
-    $(hide) $(MKDTBOIMG) cfg_create $@ $(KERNEL_OUT)/$(BOARD_KERNEL_DTBO_CFG) -d /
-    $(hide) chmod a+r $@
-endef
-
-define append-dtboimage-certs
-    $(call pretty,"Target signed dtbo image: $(BOARD_PREBUILT_DTBOIMAGE)")
-    $(hide) mv $(BOARD_PREBUILT_DTBOIMAGE) $(BOARD_PREBUILT_DTBOIMAGE).tmp
-    $(hide) $(APPEND_CERTS) --image $(BOARD_PREBUILT_DTBOIMAGE).tmp --cert1 \
-        $(DEVICE_PATH)/dtbo/cert1.der --cert2 $(DEVICE_PATH)/dtbo/cert2.der --output $(BOARD_PREBUILT_DTBOIMAGE)
-    $(hide) chmod a+r $@
-endef
-
-
-$(BOARD_PREBUILT_DTBOIMAGE): $(MKDTBOIMG) $(INSTALLED_KERNEL_TARGET)
-	$(build-dtboimage-target-from-cfg)
-	$(append-dtboimage-certs)
+BOARD_DTBO_CFG := $(DTBO_OUT)/dtboimg.cfg
+MKDTIMG := $(HOST_OUT_EXECUTABLES)/mkdtimg$(HOST_EXECUTABLE_SUFFIX)
+MKDTBOIMG := $(HOST_OUT_EXECUTABLES)/mkdtboimg.py$(HOST_EXECUTABLE_SUFFIX)
+
+$(BOARD_PREBUILT_DTBOIMAGE): $(DTC) $(MKDTIMG) $(MKDTBOIMG)
+$(BOARD_PREBUILT_DTBOIMAGE):
+	@echo "Building dtbo.img"
+	$(call make-dtbo-target,$(KERNEL_DEFCONFIG))
+	$(call make-dtbo-target,dtbs)
+	$(MKDTBOIMG) cfg_create $@ $(BOARD_DTBO_CFG) -d $(DTBO_OUT)/arch/$(KERNEL_ARCH)/boot/dts
+	$(APPEND_CERTS) --alignment 16 --cert1 $(DEVICE_PATH)/dtbo/cert1.der --cert2 $(DEVICE_PATH)/dtbo/cert2.der --dtbo $(BOARD_PREBUILT_DTBOIMAGE)