diff --git a/ChangeLog b/ChangeLog
index 7969356c1f..69dfc40c1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Apr  9 18:01:36 2011  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/util.h: parenthesize macro arguments.
+
 Fri Apr  8 16:01:56 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* ext/stringio/stringio.c (strio_getline): check whether str is
diff --git a/include/ruby/util.h b/include/ruby/util.h
index b025fb61ec..40f044d3cb 100644
--- a/include/ruby/util.h
+++ b/include/ruby/util.h
@@ -49,9 +49,9 @@ extern "C" {
 #pragma GCC visibility push(default)
 #endif
 
-#define scan_oct(s,l,e) (int)ruby_scan_oct(s,l,e)
+#define scan_oct(s,l,e) ((int)ruby_scan_oct((s),(l),(e)))
 unsigned long ruby_scan_oct(const char *, size_t, size_t *);
-#define scan_hex(s,l,e) (int)ruby_scan_hex(s,l,e)
+#define scan_hex(s,l,e) ((int)ruby_scan_hex((s),(l),(e)))
 unsigned long ruby_scan_hex(const char *, size_t, size_t *);
 
 #if defined(__CYGWIN32__) || defined(_WIN32)
@@ -65,7 +65,7 @@ void ruby_setenv(const char *, const char *);
 void ruby_unsetenv(const char *);
 #undef setenv
 #undef unsetenv
-#define setenv(name,val) ruby_setenv(name,val)
+#define setenv(name,val) ruby_setenv((name),(val))
 #define unsetenv(name,val) ruby_unsetenv(name);
 
 char *ruby_strdup(const char *);
@@ -77,7 +77,7 @@ char *ruby_getcwd(void);
 
 double ruby_strtod(const char *, char **);
 #undef strtod
-#define strtod(s,e) ruby_strtod(s,e)
+#define strtod(s,e) ruby_strtod((s),(e))
 
 #if defined _MSC_VER && _MSC_VER >= 1300
 #pragma warning(push)