diff --git a/tools/releasetools/check_target_files_signatures.py b/tools/releasetools/check_target_files_signatures.py
index 4b0d4c7..9b76954 100755
--- a/tools/releasetools/check_target_files_signatures.py
+++ b/tools/releasetools/check_target_files_signatures.py
@@ -168,7 +168,6 @@
 
 
 class APK(object):
-
   def __init__(self, full_filename, filename):
     self.filename = filename
     self.certs = None
@@ -245,12 +244,12 @@
     # must decompress them individually before we perform any analysis.
 
     # This is the list of wildcards of files we extract from |filename|.
-    apk_extensions = ['*.apk', '*.apex']
+    apk_extensions = ['*.apk']
 
     self.certmap, compressed_extension = common.ReadApkCerts(
-        zipfile.ZipFile(filename))
+        zipfile.ZipFile(filename, "r"))
     if compressed_extension:
-      apk_extensions.append('*.apk' + compressed_extension)
+      apk_extensions.append("*.apk" + compressed_extension)
 
     d = common.UnzipTemp(filename, apk_extensions)
     self.apks = {}
@@ -273,7 +272,7 @@
           os.remove(os.path.join(dirpath, fn))
           fn = uncompressed_fn
 
-        if fn.endswith(('.apk', '.apex')):
+        if fn.endswith(".apk"):
           fullname = os.path.join(dirpath, fn)
           displayname = fullname[len(d)+1:]
           apk = APK(fullname, displayname)