diff --git a/features/testbot/alternative.feature b/features/testbot/alternative.feature
index 2fc260265..40bbad5da 100644
--- a/features/testbot/alternative.feature
+++ b/features/testbot/alternative.feature
@@ -4,6 +4,14 @@ Feature: Alternative route
     Background:
         Given the profile "testbot"
         And a grid size of 200 meters
+        # Force data preparation to single-threaded to ensure consistent
+        # results for alternative generation during tests (alternative
+        # finding is highly sensitive to graph shape, which is in turn
+        # affected by parallelism during generation)
+        And the contract extra arguments "--threads 1"
+        And the extract extra arguments "--threads 1"
+        And the customize extra arguments "--threads 1"
+        And the partition extra arguments "--threads 1"
 
         And the node map
             """
diff --git a/features/testbot/alternative_loop.feature b/features/testbot/alternative_loop.feature
index dde3632a9..182137969 100644
--- a/features/testbot/alternative_loop.feature
+++ b/features/testbot/alternative_loop.feature
@@ -4,6 +4,14 @@ Feature: Alternative route
     Background:
         Given the profile "testbot"
         Given a grid size of 200 meters
+        # Force data preparation to single-threaded to ensure consistent
+        # results for alternative generation during tests (alternative
+        # finding is highly sensitive to graph shape, which is in turn
+        # affected by parallelism during generation)
+        And the contract extra arguments "--threads 1"
+        And the extract extra arguments "--threads 1"
+        And the customize extra arguments "--threads 1"
+        And the partition extra arguments "--threads 1"
 
     Scenario: Alternative Loop Paths
         Given the node map