diff --git a/toolkit/components/telemetry/tests/marionette/harness/telemetry_harness/runner.py b/toolkit/components/telemetry/tests/marionette/harness/telemetry_harness/runner.py
index 3fa1516a74fe..140c52bc56d9 100644
--- a/toolkit/components/telemetry/tests/marionette/harness/telemetry_harness/runner.py
+++ b/toolkit/components/telemetry/tests/marionette/harness/telemetry_harness/runner.py
@@ -25,6 +25,10 @@ class TelemetryTestRunner(BaseMarionetteTestRunner):
         # Set Firefox Client Telemetry specific preferences
         prefs.update(
             {
+                # Fake the geoip lookup to always return Germany to:
+                #   * avoid net access in tests
+                #   * stabilize browser.search.region to avoid an extra subsession (bug 1545207)
+                "browser.search.geoip.url": "data:application/json,{\"country_code\": \"DE\"}",
                 "toolkit.telemetry.server": "{}/pings".format(SERVER_URL),
                 "toolkit.telemetry.initDelay": 1,
                 "toolkit.telemetry.minSubsessionLength": 0,