diff --git a/artiq/devices/lda/driver.py b/artiq/devices/lda/driver.py
index 4e6742e2e..3f5aaa2e2 100644
--- a/artiq/devices/lda/driver.py
+++ b/artiq/devices/lda/driver.py
@@ -26,6 +26,10 @@ class Ldasim:
     def get_att_step_size(self):
         return self._att_step_size
 
+    def close(self):
+        """Close the device."""
+        pass
+
     def get_attenuation(self):
         """Reads last attenuation value set to the simulated device.
 
diff --git a/artiq/devices/thorlabs_tcube/driver.py b/artiq/devices/thorlabs_tcube/driver.py
index f7bac7221..8643c388e 100644
--- a/artiq/devices/thorlabs_tcube/driver.py
+++ b/artiq/devices/thorlabs_tcube/driver.py
@@ -211,6 +211,10 @@ class Tcube:
         self.port.flush()
         logger.debug("baud rate set to 115200")
 
+    def close(self):
+        """Close the device."""
+        self.port.close()
+
     def send(self, msg):
         msg.send(self.port)
 
diff --git a/artiq/frontend/lda_controller.py b/artiq/frontend/lda_controller.py
index 225700cca..27714870f 100755
--- a/artiq/frontend/lda_controller.py
+++ b/artiq/frontend/lda_controller.py
@@ -27,8 +27,11 @@ def main():
         lda = Ldasim()
     else:
         lda = Lda(args.serial, args.product)
-    simple_server_loop({"lda": lda},
-                       args.bind, args.port)
+    try:
+        simple_server_loop({"lda": lda},
+                           args.bind, args.port)
+    finally:
+        lda.close()
 
 if __name__ == "__main__":
     main()
diff --git a/artiq/frontend/thorlabs_tcube_controller.py b/artiq/frontend/thorlabs_tcube_controller.py
index bc5c32e23..90dbb12c3 100755
--- a/artiq/frontend/thorlabs_tcube_controller.py
+++ b/artiq/frontend/thorlabs_tcube_controller.py
@@ -37,7 +37,10 @@ def main():
         elif args.product == "TPZ001":
             dev = Tpz(args.device)
 
-    simple_server_loop({args.product.lower(): dev}, args.bind, args.port)
+    try:
+        simple_server_loop({args.product.lower(): dev}, args.bind, args.port)
+    finally:
+        dev.close()
 
 if __name__ == "__main__":
     main()