diff --git a/ChangeLog b/ChangeLog
index 406e275a57..bcee27d960 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Sep  2 12:28:38 2013  Tanaka Akira  <akr@fsij.org>
+
+	* test/ruby/test_bignum.rb (test_interrupt_during_to_s): Disable it
+	  when GMP is used.
+
 Mon Sep  2 07:02:10 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (Init_Bignum): Define Bignum::GMP_VERSION when GMP is used.
diff --git a/test/ruby/test_bignum.rb b/test/ruby/test_bignum.rb
index c2f8738246..5a91a2a6b6 100644
--- a/test/ruby/test_bignum.rb
+++ b/test/ruby/test_bignum.rb
@@ -577,6 +577,9 @@ class TestBignum < Test::Unit::TestCase
   end
 
   def test_interrupt_during_to_s
+    if defined?(Bignum::GMP_VERSION)
+      return # GMP doesn't support interrupt during an operation.
+    end
     time = Time.now
     start_flag = false
     end_flag = false