diff --git a/string.c b/string.c
index c63f59a..ed02111 100644
--- a/string.c
+++ b/string.c
@@ -2382,29 +2382,27 @@ rb_str_eql(VALUE str1, VALUE str2)
 static VALUE
 rb_str_cmp_m(VALUE str1, VALUE str2)
 {
-    long result;
+    int result;
+    VALUE tmp;
 
-    if (!RB_TYPE_P(str2, T_STRING)) {
-	if (!rb_respond_to(str2, rb_intern("to_str"))) {
-	    return Qnil;
-	}
-	else if (!rb_respond_to(str2, rb_intern("<=>"))) {
-	    return Qnil;
-	}
+    if (RB_TYPE_P(str2, T_STRING)) {
+	result = rb_str_cmp(str1, str2);
+    }
+    else {
+        tmp = rb_check_funcall(str2, rb_intern("to_str"), 0, 0);
+	if (tmp != Qundef && RB_TYPE_P(tmp, T_STRING)) {
+            result = rb_str_cmp(str1, tmp);
+        }
 	else {
-	    VALUE tmp = rb_funcall(str2, rb_intern("<=>"), 1, str1);
-
+            tmp = rb_funcall(str2, rb_intern("<=>"), 1, str1);
 	    if (NIL_P(tmp)) return Qnil;
-	    if (!FIXNUM_P(tmp)) {
-		return rb_funcall(LONG2FIX(0), '-', 1, tmp);
-	    }
-	    result = -FIX2LONG(tmp);
+
+            result = -rb_cmpint(tmp, str1, str2);
 	}
     }
-    else {
-	result = rb_str_cmp(str1, str2);
-    }
-    return LONG2NUM(result);
+    if (result == 0) return INT2FIX(0);
+    if (result > 0) return INT2FIX(1);
+    return INT2FIX(-1);
 }
 
 /*
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 9f63847..cbad9a1 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -170,8 +170,9 @@ class TestString < Test::Unit::TestCase
 
     o = Object.new
     def o.to_str; "bar"; end
-    assert_nil("foo" <=> o)
+    assert_equal(1, "foo" <=> o)
 
+    class << o;remove_method :to_str;end
     def o.<=>(x); nil; end
     assert_nil("foo" <=> o)
 
@@ -181,7 +182,7 @@ class TestString < Test::Unit::TestCase
 
     class << o;remove_method :<=>;end
     def o.<=>(x); 2**100; end
-    assert_equal(-(2**100), "foo" <=> o)
+    assert_equal(-1, "foo" <=> o)
   end
 
   def test_EQUAL # '=='