diff --git a/ChangeLog b/ChangeLog
index 6437ac91db..126cac520a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Sep 22 04:47:37 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/bigdecimal/bigdecimal.c (GetVpValue): support conversion from
+	  Rational.  [ruby-core:25697]
+
 Tue Sep 22 04:43:42 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* Makefile.in, win32/Makefile.sub (INSNS): depend on tools.
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 97d1822e0d..4e60bae173 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -239,9 +239,24 @@ GetVpValue(VALUE v, int must)
     Real *pv;
     VALUE bg;
     char szD[128];
+    VALUE orig = Qundef;
+    int util_loaded = 0;
 
+again:
     switch(TYPE(v))
     {
+    case T_RATIONAL:
+        if(orig == Qundef ? (orig = v, 1) : orig != v) {
+            if(!util_loaded) {
+                rb_require("bigdecimal/util");
+                util_loaded = 1;
+            }
+            v = rb_funcall2(v, rb_intern("to_d"), 0, 0);
+            goto again;
+        }
+        v = orig;
+        goto SomeOneMayDoIt;
+
     case T_DATA:
         if(rb_typeddata_is_kind_of(v, &BigDecimal_data_type)) {
             pv = DATA_PTR(v);
diff --git a/test/bigdecimal/test_bigdecimal.rb b/test/bigdecimal/test_bigdecimal.rb
index 7eecc1ade1..2490c8469c 100644
--- a/test/bigdecimal/test_bigdecimal.rb
+++ b/test/bigdecimal/test_bigdecimal.rb
@@ -691,4 +691,8 @@ class TestBigDecimal < Test::Unit::TestCase
     assert_equal(BigDecimal::SIGN_POSITIVE_ZERO, BigDecimal.new("1E-1" + "0" * 10000).sign)
     assert_equal(BigDecimal::SIGN_NEGATIVE_ZERO, BigDecimal.new("-1E-1" + "0" * 10000).sign)
   end
+
+  def test_coerce
+    assert_equal(2, 1 + BigDecimal.new("1"), '[ruby-core:25697]')
+  end
 end