diff --git a/ChangeLog b/ChangeLog
index 045a5bddea..44405ab7b7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Mar 12 09:43:11 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* complex.c (f_signbit): remove condition for signbit because
+	  all platforms have signbit from r26871.
+
 Fri Mar 12 07:25:16 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* win32/win32.c (init_env): get rid of alloca() for outer string.
diff --git a/complex.c b/complex.c
index eee1186d8f..64ea345862 100644
--- a/complex.c
+++ b/complex.c
@@ -1154,28 +1154,13 @@ nucomp_eql_p(VALUE self, VALUE other)
     return Qfalse;
 }
 
-#ifndef HAVE_SIGNBIT
-#ifdef signbit
-#define HAVE_SIGNBIT 1
-#endif
-#endif
-
 inline static VALUE
 f_signbit(VALUE x)
 {
     switch (TYPE(x)) {
       case T_FLOAT: {
-#ifdef HAVE_SIGNBIT
 	double f = RFLOAT_VALUE(x);
 	return f_boolcast(!isnan(f) && signbit(f));
-#else
-	char s[2];
-	double f = RFLOAT_VALUE(x);
-
-	if (isnan(f)) return Qfalse;
-	(void)snprintf(s, sizeof s, "%.0f", f);
-	return f_boolcast(s[0] == '-');
-#endif
       }
     }
     return f_negative_p(x);