diff --git a/mechanical_markdown/__init__.py b/mechanical_markdown/__init__.py
index 01d2a11..a8630b7 100644
--- a/mechanical_markdown/__init__.py
+++ b/mechanical_markdown/__init__.py
@@ -7,6 +7,6 @@
 from mechanical_markdown.recipe import Recipe as MechanicalMarkdown
 from mechanical_markdown.parsers import MarkdownAnnotationError
 
-__version__ = '0.2.0'
+__version__ = '0.2.1'
 
 __all__ = [MechanicalMarkdown, MarkdownAnnotationError]
diff --git a/mechanical_markdown/step.py b/mechanical_markdown/step.py
index 4841eac..8344bc5 100644
--- a/mechanical_markdown/step.py
+++ b/mechanical_markdown/step.py
@@ -79,7 +79,7 @@ def wait_for_all_background_commands(self):
         for command in self.commands:
             if self.background:
                 command.wait_or_timeout(self.timeout)
-                if command.return_code != self.expect_return_code:
+                if self.expect_return_code is not None and command.return_code != self.expect_return_code:
                     success = False
         return success