diff --git a/dangerzone/isolation_provider/base.py b/dangerzone/isolation_provider/base.py
index f39cacb42..d687fc03c 100644
--- a/dangerzone/isolation_provider/base.py
+++ b/dangerzone/isolation_provider/base.py
@@ -314,7 +314,9 @@ def doc_to_pixels_proc(
         """Start a conversion process, pass it to the caller, and then clean it up."""
         p = self.start_doc_to_pixels_proc(document)
         if platform.system() != "Windows":
-            assert os.getpgid(p.pid) != os.getpgid(os.getpid()), "Parent shares same PGID with child"
+            assert os.getpgid(p.pid) != os.getpgid(
+                os.getpid()
+            ), "Parent shares same PGID with child"
 
         try:
             yield p