diff --git a/scripts/west_commands/runners/bossac.py b/scripts/west_commands/runners/bossac.py
index fcbd6fdf92b..ff4478f1e1f 100644
--- a/scripts/west_commands/runners/bossac.py
+++ b/scripts/west_commands/runners/bossac.py
@@ -102,8 +102,7 @@ class BossacBinaryRunner(ZephyrBinaryRunner):
         b = pathlib.Path(self.cfg.build_dir)
         edt_pickle = b / 'zephyr' / 'edt.pickle'
         if not edt_pickle.is_file():
-            error_msg = "can't load devicetree; expected to find:" \
-	                + str(edt_pickle)
+            error_msg = "can't load devicetree; expected to find:" + str(edt_pickle)
 
             raise RuntimeError(error_msg)