diff --git a/ChangeLog b/ChangeLog
index 1a5771c40c..68db002dd4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Dec 21 16:18:17 2001  Nobuyoshi Nakada  <nobu.nakada@nifty.ne.jp>
+
+	* dln.h, ruby.h, util.h: enable prototypes in C++.
+
 Fri Dec 21 03:15:52 2001  Nobuyoshi Nakada  <nobu.nakada@nifty.ne.jp>
 
 	* eval.c (rb_mod_define_method): must not convert Method to Proc.
diff --git a/dln.h b/dln.h
index 1a7e002551..c6f9654eb6 100644
--- a/dln.h
+++ b/dln.h
@@ -13,6 +13,15 @@
 #ifndef DLN_H
 #define DLN_H
 
+#ifdef __cplusplus
+# ifndef  HAVE_PROTOTYPES
+#  define HAVE_PROTOTYPES 1
+# endif
+# ifndef  HAVE_STDARG_PROTOTYPES
+#  define HAVE_STDARG_PROTOTYPES 1
+# endif
+#endif
+
 #undef _
 #ifdef HAVE_PROTOTYPES
 # define _(args) args
diff --git a/ruby.h b/ruby.h
index e5ff9769e4..4de8b88746 100644
--- a/ruby.h
+++ b/ruby.h
@@ -52,6 +52,15 @@ extern "C" {
 # define volatile
 #endif
 
+#ifdef __cplusplus
+# ifndef  HAVE_PROTOTYPES
+#  define HAVE_PROTOTYPES 1
+# endif
+# ifndef  HAVE_STDARG_PROTOTYPES
+#  define HAVE_STDARG_PROTOTYPES 1
+# endif
+#endif
+
 #undef _
 #ifdef HAVE_PROTOTYPES
 # define _(args) args
@@ -582,7 +591,7 @@ EXTERN VALUE rb_eLoadError;
 EXTERN VALUE rb_defout, rb_stdin, rb_stdout, rb_stderr, ruby_errinfo;
 
 static inline VALUE
-#if defined(__cplusplus)
+#if defined(HAVE_PROTOTYPES)
 rb_class_of(VALUE obj)
 #else
 rb_class_of(obj)
@@ -599,7 +608,7 @@ rb_class_of(obj)
 }
 
 static inline int
-#if defined(__cplusplus)
+#if defined(HAVE_PROTOTYPES)
 rb_type(VALUE obj)
 #else
 rb_type(obj)
@@ -616,7 +625,7 @@ rb_type(obj)
 }
 
 static inline int
-#if defined(__cplusplus)
+#if defined(HAVE_PROTOTYPES)
 rb_special_const_p(VALUE obj)
 #else
 rb_special_const_p(obj)
diff --git a/util.h b/util.h
index 60e0ff4f60..51f32d0179 100644
--- a/util.h
+++ b/util.h
@@ -14,6 +14,14 @@
 #define UTIL_H
 
 #ifndef _
+#ifdef __cplusplus
+# ifndef  HAVE_PROTOTYPES
+#  define HAVE_PROTOTYPES 1
+# endif
+# ifndef  HAVE_STDARG_PROTOTYPES
+#  define HAVE_STDARG_PROTOTYPES 1
+# endif
+#endif
 #ifdef HAVE_PROTOTYPES
 # define _(args) args
 #else