diff --git a/test/ruby/test_rand.rb b/test/ruby/test_rand.rb
index ed74c5b211..e22e532c53 100644
--- a/test/ruby/test_rand.rb
+++ b/test/ruby/test_rand.rb
@@ -398,7 +398,7 @@ END
         raise 'default seed is not set' if srand == 0
     end
     p2, st = Process.waitpid2(pid)
-    assert(st.success?)
+    assert(st.success?, "#{st.inspect}")
   rescue NotImplementedError, ArgumentError
   end