diff --git a/package_manager/__init__.py b/package_manager/__init__.py
index 4065716..1fb04ce 100644
--- a/package_manager/__init__.py
+++ b/package_manager/__init__.py
@@ -107,10 +107,6 @@ class SubprocMixin:
 
     def quit(self):
         """Signals the state machine to stop this operator from running."""
-        try:
-            self.cancel(bpy.context)
-        except AttributeError:
-            pass
         self._state = 'QUIT'
 
     def invoke(self, context, event):
@@ -160,7 +156,6 @@ class SubprocMixin:
 
         if not self.process.is_alive():
             self.report_process_died()
-            self.cancel(context)
             self._finish(context)
             return {'CANCELLED'}
 
@@ -177,6 +172,10 @@ class SubprocMixin:
 
     def _finish(self, context):
         import multiprocessing
+        try:
+            self.cancel(context)
+        except AttributeError:
+            pass
 
         global bpkg_operation_running
 
@@ -271,7 +270,7 @@ class PACKAGE_OT_install(SubprocMixin, bpy.types.Operator):
         self.log.debug("Using %s as install path", install_path)
 
         import addon_utils
-        proc = multiprocessing.Process(target=messages.download_and_install_package,
+        proc = multiprocessing.Process(target=subproc.download_and_install_package,
                                        args=(self.pipe_subproc, package, install_path))
         return proc
 
diff --git a/package_manager/subproc.py b/package_manager/subproc.py
index e862c57..35cd529 100644
--- a/package_manager/subproc.py
+++ b/package_manager/subproc.py
@@ -26,7 +26,7 @@ def download_and_install_package(pipe_to_blender, package: bpkg.Package, install
         pipe_to_blender.send(messages.InstallError(err))
         raise
 
-    pipe_to_blender.send(Success())
+    pipe_to_blender.send(messages.Success())
 
 
 def uninstall_package(pipe_to_blender, package: bpkg.Package, install_path: Path):
@@ -41,7 +41,7 @@ def uninstall_package(pipe_to_blender, package: bpkg.Package, install_path: Path
     for pkgfile in [install_path / Path(p) for p in package.files]:
         bpkg.utils.rm(pkgfile)
 
-    pipe_to_blender.send(Success())
+    pipe_to_blender.send(messages.Success())
 
 
 def refresh_repository(pipe_to_blender, repo_storage_path: Path, repository_url: str):