diff --git a/scripts/unpack-prebuilt-apex.sh b/scripts/unpack-prebuilt-apex.sh
new file mode 100755
index 0000000..1acdeb5
--- /dev/null
+++ b/scripts/unpack-prebuilt-apex.sh
@@ -0,0 +1,59 @@
+#!/bin/bash
+
+set -eu
+
+# Copyright 2020 Google Inc. All rights reserved.
+#
+# 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.
+
+# Tool to unpack an apex file and verify that the required files were extracted.
+if [ $# -lt 5 ]; then
+  echo "usage: $0 <deapaxer_path> <debugfs_path> <apex file> <output_dir> <required_files>+" >&2
+  exit 1
+fi
+
+DEAPEXER_PATH=$1
+DEBUGFS_PATH=$2
+APEX_FILE=$3
+OUTPUT_DIR=$4
+shift 4
+REQUIRED_PATHS=$@
+
+set -x 1
+
+rm -fr $OUTPUT_DIR
+mkdir -p $OUTPUT_DIR
+
+# Unpack the apex file contents.
+$DEAPEXER_PATH --debugfs_path $DEBUGFS_PATH extract $APEX_FILE $OUTPUT_DIR
+
+# Verify that the files that the build expects to be in the .apex file actually
+# exist, and make sure they have a fresh mtime to not confuse ninja.
+typeset -i FAILED=0
+for r in $REQUIRED_PATHS; do
+  if [ ! -f $r ]; then
+    echo "Required file $r not present in apex $APEX_FILE" >&2
+    FAILED=$FAILED+1
+  else
+    # TODO(http:/b/177646343) - deapexer extracts the files with a timestamp of 1 Jan 1970.
+    # touch the file so that ninja knows it has changed.
+    touch $r
+  fi
+done
+
+if [ $FAILED -gt 0 ]; then
+  echo "$FAILED required files were missing from $APEX_FILE" >&2
+  echo "Available files are:" >&2
+  find $OUTPUT_DIR -type f | sed "s|^|    |" >&2
+  exit 1
+fi