diff --git a/artiq/master/experiments.py b/artiq/master/experiments.py
index fc27874762..bf5a905b07 100644
--- a/artiq/master/experiments.py
+++ b/artiq/master/experiments.py
@@ -64,7 +64,7 @@ async def _scan(self, root, subdir=""):
                         exc_info=not isinstance(exc, WorkerInternalException))
                     # restart worker
                     await self.worker.close()
-                    self.worker = Worker(self.worker_handlers)
+                    self.worker = self._create_worker()
             if de.is_dir():
                 subentries = await self._scan(
                     root, os.path.join(subdir, de.name))
@@ -72,10 +72,12 @@ async def _scan(self, root, subdir=""):
                 entry_dict.update(entries)
         return entry_dict
 
-    async def scan(self, root):
-        self.worker = Worker(self.worker_handlers)
+    async def scan(self, repo_path):
+        self._create_worker = lambda:  Worker(self.worker_handlers,
+                                              repo_path=repo_path)
+        self.worker = self._create_worker()
         try:
-            r = await self._scan(root)
+            r = await self._scan(repo_path)
         finally:
             await self.worker.close()
         return r
@@ -96,7 +98,7 @@ def __init__(self, repo_backend, worker_handlers):
         self.worker_handlers = worker_handlers
 
         self.cur_rev = self.repo_backend.get_head_rev()
-        self.repo_backend.request_rev(self.cur_rev)
+        self.repo_path, _ = self.repo_backend.request_rev(self.cur_rev)
         self.explist = Notifier(dict())
         self._scanning = False
 
@@ -140,7 +142,10 @@ async def examine(self, filename, use_repository=True, revision=None):
                 revision = self.cur_rev
             wd, _ = self.repo_backend.request_rev(revision)
             filename = os.path.join(wd, filename)
-        worker = Worker(self.worker_handlers)
+            repo_path = wd
+        else:
+            repo_path = self.repo_path
+        worker = Worker(self.worker_handlers, repo_path=repo_path)
         try:
             description = await worker.examine("examine", filename)
         finally:
@@ -183,7 +188,12 @@ def release_rev(self, rev):
 
 class _GitCheckout:
     def __init__(self, git, rev):
-        self.path = tempfile.mkdtemp()
+        parent_path = tempfile.mkdtemp()
+        # Checkout into a subdirectory 'repository' of our temp dir to ensure
+        # that there are no other modules unintentionally added to the python
+        # path
+        self.path = parent_path+os.path.sep+'repository'
+        os.mkdir(self.path)
         commit = git.get(rev)
         git.checkout_tree(commit, directory=self.path)
         self.message = commit.message.strip()
diff --git a/artiq/master/scheduler.py b/artiq/master/scheduler.py
index 53d06cac9f..c8e812b619 100644
--- a/artiq/master/scheduler.py
+++ b/artiq/master/scheduler.py
@@ -45,7 +45,7 @@ async def worker_method(self, *args, **kwargs):
 
 class Run:
     def __init__(self, rid, pipeline_name,
-                 wd, expid, priority, due_date, flush,
+                 wd, repo_path, expid, priority, due_date, flush,
                  pool, **kwargs):
         # called through pool
         self.rid = rid
@@ -56,7 +56,7 @@ def __init__(self, rid, pipeline_name,
         self.due_date = due_date
         self.flush = flush
 
-        self.worker = Worker(pool.worker_handlers)
+        self.worker = Worker(pool.worker_handlers, repo_path=repo_path)
         self.termination_requested = False
 
         self._status = RunStatus.pending
@@ -135,10 +135,12 @@ def submit(self, expid, priority, due_date, flush, pipeline_name):
                 expid["repo_rev"] = self.experiment_db.cur_rev
             wd, repo_msg = self.experiment_db.repo_backend.request_rev(
                 expid["repo_rev"])
+            repo_path = wd
         else:
             wd, repo_msg = None, None
-        run = Run(rid, pipeline_name, wd, expid, priority, due_date, flush,
-                  self, repo_msg=repo_msg)
+            repo_path = self.experiment_db.repo_backend.request_rev(None)
+        run = Run(rid, pipeline_name, wd, repo_path, expid, priority, due_date, 
+                  flush, self, repo_msg=repo_msg)
         self.runs[rid] = run
         self.state_changed.notify()
         return rid
diff --git a/artiq/master/worker.py b/artiq/master/worker.py
index 69b6d9a28a..81e12e0732 100644
--- a/artiq/master/worker.py
+++ b/artiq/master/worker.py
@@ -41,7 +41,7 @@ def log_worker_exception():
 
 
 class Worker:
-    def __init__(self, handlers=dict(), send_timeout=10.0):
+    def __init__(self, handlers=dict(), send_timeout=10.0, repo_path=None):
         self.handlers = handlers
         self.send_timeout = send_timeout
 
@@ -49,6 +49,7 @@ def __init__(self, handlers=dict(), send_timeout=10.0):
         self.filename = None
         self.ipc = None
         self.watchdogs = dict()  # wid -> expiration (using time.monotonic)
+        self.repo_path = repo_path
 
         self.io_lock = asyncio.Lock()
         self.closed = asyncio.Event()
@@ -85,6 +86,13 @@ async def _create_process(self, log_level):
             self.ipc = pipe_ipc.AsyncioParentComm()
             env = os.environ.copy()
             env["PYTHONUNBUFFERED"] = "1"
+            if self.repo_path:
+                # Add parent of repository directory to PYTHONPATH
+                repo_parent_path = os.path.dirname(self.repo_path)
+                if "PYTHONPATH" in env:
+                    env["PYTHONPATH"] += os.pathsep+repo_parent_path
+                else:
+                    env["PYTHONPATH"] = repo_parent_path
             await self.ipc.create_subprocess(
                 sys.executable, "-m", "artiq.master.worker_impl",
                 self.ipc.get_address(), str(log_level),