diff --git a/spec/integration/bisect_spec.rb b/spec/integration/bisect_spec.rb
index 1e2375fc4a..9c9d82ae20 100644
--- a/spec/integration/bisect_spec.rb
+++ b/spec/integration/bisect_spec.rb
@@ -45,7 +45,7 @@ def bisect(cli_args, expected_status=nil)
       it 'does not leave zombie processes', :unless => RSpec::Support::OS.windows? do
         original_pids = pids()
         bisect(%W[spec/rspec/core/resources/blocking_pipe_bisect_spec.rb_], 1)
-        sleep 0.1 while (extra_pids = pids() - original_pids).join =~ /[RE]/i
+        sleep 0.1 while ((extra_pids = pids() - original_pids).join =~ /[RE]/i)
         expect(extra_pids.join).to_not include "Z"
       end
     end