diff --git a/ChangeLog b/ChangeLog
index 57467d64d1..58a9250693 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jun 13 22:18:01 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in: remove -ansi and -std options for lgamma_r() and
+	  finite().
+
 Wed Jun 13 21:46:34 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in: cygwin does not provide some declarations in strict
diff --git a/configure.in b/configure.in
index 359564b91f..565f4754b2 100644
--- a/configure.in
+++ b/configure.in
@@ -617,8 +617,8 @@ if test "$GCC" = yes; then
       # comments.   We  bypass  ANSI   C  mode  for  them.   Otherwise
       # extension libs cannot include those headers.
     ],
-    [cygwin*], [
-      # ditto
+    [cygwin*|darwin*], [
+      # need lgamma_r(), finite()
     ],
     [
       # ANSI (no XCFLAGS because this is C only)
@@ -1116,7 +1116,7 @@ AS_CASE(["$target_os"],
 [openstep*], [	],
 [rhapsody*], [	],
 [darwin*], [	RUBY_PREPEND_OPTION(LIBS, -lobjc)
-		RUBY_APPEND_OPTIONS(CPPFLAGS, -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT)
+		RUBY_APPEND_OPTIONS(CPPFLAGS, -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT)
 		AC_MSG_CHECKING(whether Mac OS X 10.5 or later)
 		AC_TRY_CPP([#include <AvailabilityMacros.h>
 		    #if MAC_OS_X_VERSION_MAX_ALLOWED <= 1040