diff --git a/tools/signtos/Android.bp b/tools/signtos/Android.bp
new file mode 100644
index 000000000..b26631f1e
--- /dev/null
+++ b/tools/signtos/Android.bp
@@ -0,0 +1,27 @@
+//
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// the signtos tool - signs Trusty images
+// ============================================================
+java_library_host {
+    name: "signtos",
+    srcs: ["SignTos.java"],
+    manifest: "SignTos.mf",
+    static_libs: [
+        "bouncycastle",
+        "bouncycastle-bcpkix",
+    ],
+}
diff --git a/tools/signtos/Android.mk b/tools/signtos/Android.mk
deleted file mode 100644
index 3e869b38e..000000000
--- a/tools/signtos/Android.mk
+++ /dev/null
@@ -1,25 +0,0 @@
-#
-# Copyright (C) 2014 The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-LOCAL_PATH := $(call my-dir)
-
-# the signtos tool - signs Trusty images
-# ============================================================
-include $(CLEAR_VARS)
-LOCAL_MODULE := signtos
-LOCAL_SRC_FILES := SignTos.java
-LOCAL_JAR_MANIFEST := SignTos.mf
-LOCAL_STATIC_JAVA_LIBRARIES := bouncycastle bouncycastle-bcpkix
-include $(BUILD_HOST_JAVA_LIBRARY)