diff --git a/buildtest/builders/base.py b/buildtest/builders/base.py
index 0ab920129..a2214c248 100644
--- a/buildtest/builders/base.py
+++ b/buildtest/builders/base.py
@@ -169,7 +169,7 @@ def shell_detection(self):
         self.shell = Shell(
             self.recipe.get("shell")
             or self.buildexecutor.executors[self.executor]._settings.get("shell")
-            or 'bash'
+            or "bash"
         )
 
         # set shebang to value defined in Buildspec, if not defined then get one from Shell class