diff --git a/ChangeLog b/ChangeLog
index 0e42d19407..bc9b73b9cc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Nov 20 13:37:34 2003  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
+
+	* ruby.h: define is_ruby_native_thread() for no native thread 
+	  environment
+
+	* eval.c: ditto
+
 Thu Nov 20 12:42:47 2003  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* configure.in: always check existence of the pthread library
diff --git a/eval.c b/eval.c
index ecb1725cc1..597ce03c29 100644
--- a/eval.c
+++ b/eval.c
@@ -1159,11 +1159,16 @@ void Init_ext _((void));
 
 #ifdef HAVE_NATIVETHREAD
 static rb_nativethread_t ruby_thid;
+#endif
+
 int 
 is_ruby_native_thread() {
+#ifdef HAVE_NATIVETHREAD
     return NATIVETHREAD_EQUAL(ruby_thid, NATIVETHREAD_CURRENT());
-}
+#else
+    return 1;
 #endif
+}
 
 void
 ruby_init()
diff --git a/ruby.h b/ruby.h
index 7bac5db499..9818a3e149 100644
--- a/ruby.h
+++ b/ruby.h
@@ -682,9 +682,7 @@ typedef DWORD rb_nativethread_t;
 # define NATIVETHREAD_EQUAL(t1,t2) ((t1) == (t2))
 # define HAVE_NATIVETHREAD
 #endif
-#ifdef HAVE_NATIVETHREAD
 RUBY_EXTERN int is_ruby_native_thread();
-#endif
 
 #if defined(__cplusplus)
 }  /* extern "C" { */