diff --git a/lib/test_prof/recipes/minitest/sample.rb b/lib/test_prof/recipes/minitest/sample.rb
index e26b6ff5..df4fbcf3 100644
--- a/lib/test_prof/recipes/minitest/sample.rb
+++ b/lib/test_prof/recipes/minitest/sample.rb
@@ -7,14 +7,16 @@ module MinitestSample
     CORE_RUNNABLES = [
       Minitest::Test,
       defined?(Minitest::Unit::TestCase) ? Minitest::Unit::TestCase : nil,
-      Minitest::Spec
+      defined?(Minitest::Spec) ? Minitest::Spec : nil
     ].compact.freeze
 
     class << self
       def suites
         # Make sure that sample contains only _real_ suites
         Minitest::Runnable.runnables
-          .reject { |suite| CORE_RUNNABLES.include?(suite) }
+          .select do |suite|
+            CORE_RUNNABLES.any? { |kl| suite < kl } && suite.runnable_methods.any?
+          end
       end
 
       def sample_groups(sample_size)
diff --git a/spec/integrations/fixtures/minitest/sample_fixture.rb b/spec/integrations/fixtures/minitest/sample_fixture.rb
index dd0bec01..7e823f3f 100644
--- a/spec/integrations/fixtures/minitest/sample_fixture.rb
+++ b/spec/integrations/fixtures/minitest/sample_fixture.rb
@@ -14,7 +14,10 @@ def test_pass2
   end
 end
 
-class AnotherSomethingTest < Minitest::Test
+class CustomTestCase < Minitest::Test
+end
+
+class AnotherSomethingTest < CustomTestCase
   def test_pass
     assert true
   end