diff --git a/test/test_iotthinks_merge.py b/test/test_iotthinks_merge.py
index ed5108d1d..5fd448f53 100644
--- a/test/test_iotthinks_merge.py
+++ b/test/test_iotthinks_merge.py
@@ -39,7 +39,11 @@ class IotthinksMergeTests(unittest.TestCase):
         rak = self.flags("env:RAK_3401_repeater_bridge_rs232_serial1")
         tracker = self.flags("env:heltec_tracker_v2_repeater_bridge_rs232")
         self.assertIn("-D WITH_RS232_BRIDGE=Serial1", rak)
+        self.assertIn("-D WITH_RS232_BRIDGE_UART=1", rak)
+        self.assertIn("-UENV_INCLUDE_GPS", rak)
+        self.assertIn("-D ENV_INCLUDE_GPS=0", rak)
         self.assertIn("-D WITH_RS232_BRIDGE=Serial2", tracker)
+        self.assertIn("-D WITH_RS232_BRIDGE_UART=2", tracker)
         self.assertIn("-D WITH_RS232_BRIDGE_RX=44", tracker)
         self.assertIn("-D WITH_RS232_BRIDGE_TX=43", tracker)
 
diff --git a/variants/heltec_tracker_v2/platformio.ini b/variants/heltec_tracker_v2/platformio.ini
index 9fadda019..cf069a04e 100644
--- a/variants/heltec_tracker_v2/platformio.ini
+++ b/variants/heltec_tracker_v2/platformio.ini
@@ -160,6 +160,7 @@ build_flags =
   -D ADMIN_PASSWORD='"password"'
   -D MAX_NEIGHBOURS=50
   -D WITH_RS232_BRIDGE=Serial2
+  -D WITH_RS232_BRIDGE_UART=2
   -D WITH_RS232_BRIDGE_RX=44
   -D WITH_RS232_BRIDGE_TX=43
 ;  -D MESH_PACKET_LOGGING=1
diff --git a/variants/rak3401/platformio.ini b/variants/rak3401/platformio.ini
index e1ce0c76c..5c2f868db 100644
--- a/variants/rak3401/platformio.ini
+++ b/variants/rak3401/platformio.ini
@@ -154,8 +154,13 @@ build_src_filter = ${rak3401.build_src_filter}
 extends = env:RAK_3401_repeater
 build_flags =
   ${env:RAK_3401_repeater.build_flags}
+  ; This dedicated bridge owns the GPS connector's UART1. Never probe or
+  ; restart GPS on the same pins while the external serial peer is attached.
+  -UENV_INCLUDE_GPS
+  -D ENV_INCLUDE_GPS=0
   -D ADVERT_NAME='"RAK3401 1W RS232 Bridge"'
   -D WITH_RS232_BRIDGE=Serial1
+  -D WITH_RS232_BRIDGE_UART=1
   -D WITH_RS232_BRIDGE_RX=PIN_SERIAL1_RX
   -D WITH_RS232_BRIDGE_TX=PIN_SERIAL1_TX
 build_src_filter = ${env:RAK_3401_repeater.build_src_filter}