diff --git a/ChangeLog b/ChangeLog
index 70d10cff31..07cc5888b7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jun  9 23:58:12 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/Win32API/Win32API.c (Win32API_Call): disable global
+	  optimization. fixed: [ruby-core:05143]
+
 Thu Jun  9 23:35:22 2005  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* enum.c (enum_inject): default the result value to Qundef to use
diff --git a/ext/Win32API/Win32API.c b/ext/Win32API/Win32API.c
index be07b8504f..96ce8c6636 100644
--- a/ext/Win32API/Win32API.c
+++ b/ext/Win32API/Win32API.c
@@ -53,12 +53,12 @@ Win32API_initialize(self, dllname, proc, import, export)
     hdll = LoadLibrary(RSTRING(dllname)->ptr);
     if (!hdll)
 	rb_raise(rb_eRuntimeError, "LoadLibrary: %s\n", RSTRING(dllname)->ptr);
-    rb_iv_set(self, "__hdll__", Data_Wrap_Struct(rb_cData, 0, Win32API_FreeLibrary, hdll));
-    hproc = GetProcAddress(hdll, RSTRING(proc)->ptr);
+    rb_iv_set(self, "__hdll__", Data_Wrap_Struct(rb_cData, 0, Win32API_FreeLibrary, (void*)hdll));
+    hproc = (HANDLE)GetProcAddress(hdll, RSTRING(proc)->ptr);
     if (!hproc) {
 	str = rb_str_new3(proc);
 	str = rb_str_cat(str, "A", 1);
-	hproc = GetProcAddress(hdll, RSTRING(str)->ptr);
+	hproc = (HANDLE)GetProcAddress(hdll, RSTRING(str)->ptr);
 	if (!hproc)
 	    rb_raise(rb_eRuntimeError, "GetProcAddress: %s or %s\n",
 		RSTRING(proc)->ptr, RSTRING(str)->ptr);
@@ -137,6 +137,9 @@ Win32API_initialize(self, dllname, proc, import, export)
     return Qnil;
 }
 
+#ifdef _MSC_VER
+#pragma optimize("g", off)
+#endif
 static VALUE
 Win32API_Call(argc, argv, obj)
     int argc;
diff --git a/ext/Win32API/extconf.rb b/ext/Win32API/extconf.rb
index 134a6e5b92..865788556f 100644
--- a/ext/Win32API/extconf.rb
+++ b/ext/Win32API/extconf.rb
@@ -1,5 +1,6 @@
 require 'mkmf'
 
+dir_config("win32")
 if have_header("windows.h") and have_library("kernel32")
   create_makefile("Win32API")
 end