diff --git a/test/ruby/test_iseq.rb b/test/ruby/test_iseq.rb
index 54256816cf..4de2aa7169 100644
--- a/test/ruby/test_iseq.rb
+++ b/test/ruby/test_iseq.rb
@@ -186,12 +186,14 @@ class TestISeq < Test::Unit::TestCase
     assert_predicate(s4, :frozen?)
   end
 
+  # Safe call chain is not optimized when Coverage is running.
+  # So we can test it only when Coverage is not running.
   def test_safe_call_chain
     src = "a&.a&.a&.a&.a&.a"
     body = compile(src, __LINE__, {peephole_optimization: true}).to_a[13]
     labels = body.select {|op, arg| op == :branchnil}.map {|op, arg| arg}
     assert_equal(1, labels.uniq.size)
-  end
+  end if (!defined?(Coverage) || !Coverage.running?)
 
   def test_parent_iseq_mark
     assert_separately([], <<-'end;', timeout: 20)