diff --git a/teuthology/task/internal.py b/teuthology/task/internal.py
index 4c8341f9a79..fd90f7b665e 100644
--- a/teuthology/task/internal.py
+++ b/teuthology/task/internal.py
@@ -70,7 +70,7 @@ def lock_machines(ctx, config):
     try:
         yield
     finally:
-        if ctx.summary['success'] or not ctx.keep_locked_on_error:
+        if not ctx.keep_locked_on_error or ctx.summary.get('success', False):
             log.info('Unlocking machines...')
             for machine in ctx.config['targets']:
                 lock.unlock(ctx, machine, ctx.owner)