diff --git a/engine/src/flutter/tools/shelldb b/engine/src/flutter/tools/shelldb
index d64f917df6..28fbfb3cb6 100755
--- a/engine/src/flutter/tools/shelldb
+++ b/engine/src/flutter/tools/shelldb
@@ -175,7 +175,8 @@ class StartSky(object):
         pids['build_dir'] = os.path.abspath(args.build_dir)
 
         if args.install:
-            subprocess.check_call([ADB_PATH, 'install', '-r', apk_path])
+            # -r to replace an existing apk, -d to allow version downgrade.
+            subprocess.check_call([ADB_PATH, 'install', '-r', '-d', apk_path])
 
         port_string = 'tcp:%s' % sky_server.port
         subprocess.check_call([
diff --git a/engine/src/flutter/tools/skydb b/engine/src/flutter/tools/skydb
index 5b935bb9d3..e024946c68 100755
--- a/engine/src/flutter/tools/skydb
+++ b/engine/src/flutter/tools/skydb
@@ -226,7 +226,8 @@ class SkyDebugger(object):
             subprocess.check_call([ADB_PATH, 'root'])
 
             # We could make installing conditional on an argument.
-            subprocess.check_call([ADB_PATH, 'install', '-r', apk_path])
+            # -r to replace an existing apk, -d to allow version downgrade.
+            subprocess.check_call([ADB_PATH, 'install', '-r', '-d', apk_path])
 
             port_string = 'tcp:%s' % sky_server.port
             subprocess.check_call([