diff --git a/artiq/browser/experiments.py b/artiq/browser/experiments.py
index ebe64ef6d..5e984469b 100644
--- a/artiq/browser/experiments.py
+++ b/artiq/browser/experiments.py
@@ -176,7 +176,6 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
         self.layout.setRowStretch(0, 1)
 
         self.options = {"log_level": logging.WARNING}
-        self._worker = None
         self._run_task = None
 
         log_level = QtWidgets.QComboBox()
@@ -206,6 +205,7 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
                           QtWidgets.QSizePolicy.Expanding)
         self.layout.addWidget(run, 1, 4, 2, 1)
         run.clicked.connect(self.run_clicked)
+        self._run = run
 
         terminate = QtWidgets.QPushButton("Terminate")
         terminate.setIcon(QtWidgets.QApplication.style().standardIcon(
@@ -216,6 +216,8 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
                                 QtWidgets.QSizePolicy.Expanding)
         self.layout.addWidget(terminate, 3, 4)
         terminate.clicked.connect(self.terminate_clicked)
+        terminate.setEnabled(False)
+        self._terminate = terminate
 
     def dragEnterEvent(self, ev):
         if ev.mimeData().hasFormat("text/uri-list"):
@@ -265,9 +267,6 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
         await self._recompute_arguments(arguments)
 
     def run_clicked(self):
-        if self._run_task is not None:
-            logger.error("Analysis already started")
-            return
         class_name, file = self.expurl.split("@", maxsplit=1)
         expid = {
             "repo_rev": "N/A",
@@ -280,32 +279,32 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
                 for name, argument in self.arguments.items()},
         }
         self._run_task = asyncio.ensure_future(self._get_run_task(expid))
+        self._run.setEnabled(False)
+        self._terminate.setEnabled(True)
 
         def done(fut):
             logger.info("Analysis done")
             self._run_task = None
-
+            self._run.setEnabled(True)
+            self._terminate.setEnabled(False)
         self._run_task.add_done_callback(done)
 
     async def _get_run_task(self, expid):
-        self._worker = Worker(self._area.worker_handlers)
+        worker = Worker(self._area.worker_handlers)
         try:
-            await self._worker.build(rid=None, pipeline_name="browser",
-                                     wd=os.path.abspath("."),
-                                     expid=expid, priority=0)
-            await self._worker.analyze()
+            await worker.build(rid=None, pipeline_name="browser",
+                               wd=os.path.abspath("."),
+                               expid=expid, priority=0)
+            await worker.analyze()
         except:
             # May happen when experiment has been removed
             # from repository/explist
             logger.error("Failed to run '%s'",
                          self.expurl, exc_info=True)
         finally:
-            await self._worker.close()
-            self._worker = None
+            await worker.close()
 
     def terminate_clicked(self):
-        if self._run_task is None:
-            return
         try:
             self._run_task.cancel()
         except: