diff --git a/src/mr/developer/common.py b/src/mr/developer/common.py
index 6520ec7..b737514 100644
--- a/src/mr/developer/common.py
+++ b/src/mr/developer/common.py
@@ -168,7 +168,8 @@ def worker(working_copies, the_queue):
             return
         try:
             output = action(**kwargs)
-        except WCError:
+        except WCError as e:
+            threading.current_thread().exc = e
             output_lock.acquire()
             for lvl, msg in wc._output:
                 lvl(msg)
@@ -259,6 +260,12 @@ def _cleanup():
                 thread.start()
                 threads.append(thread)
             for thread in threads:
+                exc = None
+                if hasattr(thread, "exc"):
+                    exc = thread.exc
+                    delattr(thread, "exc")
+                if exc:
+                    raise thread.exc
                 thread.join()
             if sys.version_info < (2, 6):
                 subprocess._cleanup = _old_subprocess_cleanup
diff --git a/src/mr/developer/git.py b/src/mr/developer/git.py
index 0ed6fa8..87e7b70 100644
--- a/src/mr/developer/git.py
+++ b/src/mr/developer/git.py
@@ -199,8 +199,7 @@ def git_switch_branch(self, stdout_in, stderr_in, accept_missing=False):
             return (stdout_in + stdout,
                     stderr_in + stderr)
         else:
-            self.output((logger.error, "No such branch %r", branch))
-            sys.exit(1)
+            raise GitError("No such branch %r" % branch)
         # runs the checkout with predetermined arguments
         cmd = self.run_git(argv, cwd=path)
         stdout, stderr = cmd.communicate()
@@ -288,7 +287,10 @@ def matches(self):
     def update(self, **kwargs):
         name = self.source['name']
         if not self.matches():
-            self.output((logger.warning, "Can't update package '%s' because its URL doesn't match." % name))
+            message = "Can't update package '%s' because its URL doesn't match." % name
+            if kwargs.get("force"):
+                raise GitError(message)
+            self.output((logger.warning, message))
         if self.status() != 'clean' and not kwargs.get('force', False):
             raise GitError("Can't update package '%s' because it's dirty." % name)
         return self.git_update(**kwargs)