diff --git a/ruby/lib/ci/queue/redis/worker.rb b/ruby/lib/ci/queue/redis/worker.rb
index 542f029d..9e37528f 100644
--- a/ruby/lib/ci/queue/redis/worker.rb
+++ b/ruby/lib/ci/queue/redis/worker.rb
@@ -200,11 +200,17 @@ def try_to_reserve_lost_test
           lost_test
         end
 
+        QueueNotEmptyError = Class.new(StandardError)
+
         def push(tests)
           @total = tests.size
 
           if @master = redis.setnx(key('master-status'), 'setup')
-            puts "Worker electected as leader, pushing #{@total} tests to the queue."
+            current_length = redis.llen(key('queue'))
+
+            raise QueueNotEmptyError, "Queue is not empty (#{current_length})" if current_length > 0
+
+            puts "Worker electected as leader, pushing #{@total} tests to the queue (#{current_length})."
             puts
 
             duration = measure do
diff --git a/ruby/test/integration/rspec_redis_test.rb b/ruby/test/integration/rspec_redis_test.rb
index a459e688..4640d795 100644
--- a/ruby/test/integration/rspec_redis_test.rb
+++ b/ruby/test/integration/rspec_redis_test.rb
@@ -34,7 +34,7 @@ def test_redis_runner
 
       assert_empty err
       expected_output = strip_heredoc <<-EOS
-        Worker electected as leader, pushing 3 tests to the queue.
+        Worker electected as leader, pushing 3 tests to the queue (0).
 
         Finished pushing 3 tests to the queue in X.XXs.
 
@@ -91,7 +91,7 @@ def test_redis_runner_retry
 
       assert_empty err
       expected_output = strip_heredoc <<-EOS
-        Worker electected as leader, pushing 3 tests to the queue.
+        Worker electected as leader, pushing 3 tests to the queue (0).
 
         Finished pushing 3 tests to the queue in X.XXs.
 
@@ -273,7 +273,7 @@ def test_before_suite_errors
 
       assert_empty err
       expected_output = strip_heredoc <<-EOS
-        Worker electected as leader, pushing 2 tests to the queue.
+        Worker electected as leader, pushing 2 tests to the queue (0).
 
         Finished pushing 2 tests to the queue in X.XXs.
 
@@ -317,7 +317,7 @@ def test_report
 
       assert_empty err
       expected_output = strip_heredoc <<-EOS
-        Worker electected as leader, pushing 3 tests to the queue.
+        Worker electected as leader, pushing 3 tests to the queue (0).
 
         Finished pushing 3 tests to the queue in X.XXs.
 
@@ -418,7 +418,7 @@ def test_world_wants_to_quit
 
       assert_empty err
       expected_output = strip_heredoc <<-EOS
-        Worker electected as leader, pushing 1 tests to the queue.
+        Worker electected as leader, pushing 1 tests to the queue (0).
 
         Finished pushing 1 tests to the queue in X.XXs.