diff --git a/include/msvcrt/process.h b/include/msvcrt/process.h
index 376ecc937c8..aa53d39de4b 100644
--- a/include/msvcrt/process.h
+++ b/include/msvcrt/process.h
@@ -34,12 +34,25 @@ typedef unsigned short MSVCRT(wchar_t);
 #define _WAIT_CHILD      0
 #define _WAIT_GRANDCHILD 1
 
+#ifndef __stdcall
+# ifdef __i386__
+#  ifdef __GNUC__
+#   define __stdcall __attribute__((__stdcall__))
+#  elif defined(_MSC_VER)
+    /* Nothing needs to be done. __stdcall already exists */
+#  else
+#   error You need to define __stdcall for your compiler
+#  endif
+# else  /* __i386__ */
+#  define __stdcall
+# endif  /* __i386__ */
+#endif /* __stdcall */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-typedef void (__cdecl *_beginthread_start_routine_t)(void *);
+typedef void (*_beginthread_start_routine_t)(void *);
 typedef unsigned int (__stdcall *_beginthreadex_start_routine_t)(void *);
 
 unsigned long _beginthread(_beginthread_start_routine_t,unsigned int,void*);
diff --git a/include/windef.h b/include/windef.h
index daf3e22397e..4e9de1495b8 100644
--- a/include/windef.h
+++ b/include/windef.h
@@ -41,22 +41,31 @@ extern "C" {
 
 /* Calling conventions definitions */
 
-#ifdef __i386__
-# ifndef _X86_
-#  define _X86_
+#if defined(__i386__) && !defined(_X86_)
+# define _X86_
+#endif
+
+#ifndef __stdcall
+# ifdef __i386__
+#  ifdef __GNUC__
+#   define __stdcall __attribute__((__stdcall__))
+#  elif defined(_MSC_VER)
+    /* Nothing needs to be done. __stdcall already exists */
+#  else
+#   error You need to define __stdcall for your compiler
+#  endif
+# else  /* __i386__ */
+#  define __stdcall
+# endif  /* __i386__ */
+#endif /* __stdcall */
+
+#ifndef __cdecl
+# if defined(__i386__) && defined(__GNUC__)
+#  define __cdecl __attribute__((__cdecl__))
+# elif !defined(_MSC_VER)
+#  define __cdecl
 # endif
-# if defined(__GNUC__) && ((__GNUC__ > 2) || ((__GNUC__ == 2) && (__GNUC_MINOR__ >= 7)))
-#  define __stdcall __attribute__((__stdcall__))
-#  define __cdecl   __attribute__((__cdecl__))
-# elif defined(_MSC_VER)
-/* Nothing needs to be done. __cdecl/__stdcall already exists */
-# else
-#  error You need gcc >= 2.7 to build Wine on a 386
-# endif  /* __GNUC__ */
-#else  /* __i386__ */
-# define __stdcall
-# define __cdecl
-#endif  /* __i386__ */
+#endif /* __stdcall */
 
 #ifndef __WINESRC__