diff --git a/tools/winebuild/spec32.c b/tools/winebuild/spec32.c
index 09bb636c987..9dd436b8901 100644
--- a/tools/winebuild/spec32.c
+++ b/tools/winebuild/spec32.c
@@ -509,19 +509,31 @@ void BuildSpec32File( FILE *outfile )
     case SPEC_MODE_GUIEXE:
         if (!init_func) init_func = "WinMain";
         fprintf( outfile,
-                 "\n#include <winbase.h>\n"
+                 "\ntypedef struct {\n"
+                 "    unsigned int cb;\n"
+                 "    char *lpReserved, *lpDesktop, *lpTitle;\n"
+                 "    unsigned int dwX, dwY, dwXSize, dwYSize;\n"
+                 "    unsigned int dwXCountChars, dwYCountChars, dwFillAttribute, dwFlags;\n"
+                 "    unsigned short wShowWindow, cbReserved2;\n"
+                 "    char *lpReserved2;\n"
+                 "    void *hStdInput, *hStdOutput, *hStdError;\n"
+                 "} STARTUPINFOA;\n"
                  "int _ARGC;\n"
                  "char **_ARGV;\n"
-                 "extern int __stdcall %s(HINSTANCE,HINSTANCE,LPSTR,INT);\n"
+                 "extern int __stdcall %s(void *,void *,char *,int);\n"
+                 "extern char * __stdcall GetCommandLineA(void);\n"
+                 "extern void * __stdcall GetModuleHandleA(char *);\n"
+                 "extern void __stdcall GetStartupInfoA(STARTUPINFOA *);\n"
+                 "extern void __stdcall ExitProcess(unsigned int);\n"
                  "static void __wine_exe_main(void)\n"
                  "{\n"
                  "    extern int __wine_get_main_args( char ***argv );\n"
                  "    STARTUPINFOA info;\n"
-                 "    LPSTR cmdline = GetCommandLineA();\n"
+                 "    char *cmdline = GetCommandLineA();\n"
                  "    while (*cmdline && *cmdline != ' ') cmdline++;\n"
                  "    if (*cmdline) cmdline++;\n"
                  "    GetStartupInfoA( &info );\n"
-                 "    if (!(info.dwFlags & STARTF_USESHOWWINDOW)) info.wShowWindow = 1;\n"
+                 "    if (!(info.dwFlags & 1)) info.wShowWindow = 1;\n"
                  "    _ARGC = __wine_get_main_args( &_ARGV );\n"
                  "    ExitProcess( %s( GetModuleHandleA(0), 0, cmdline, info.wShowWindow ) );\n"
                  "}\n\n", init_func, init_func );
@@ -531,19 +543,32 @@ void BuildSpec32File( FILE *outfile )
     case SPEC_MODE_GUIEXE_UNICODE:
         if (!init_func) init_func = "WinMain";
         fprintf( outfile,
-                 "\n#include <winbase.h>\n"
+                 "\ntypedef unsigned short WCHAR;\n"
+                 "typedef struct {\n"
+                 "    unsigned int cb;\n"
+                 "    char *lpReserved, *lpDesktop, *lpTitle;\n"
+                 "    unsigned int dwX, dwY, dwXSize, dwYSize;\n"
+                 "    unsigned int dwXCountChars, dwYCountChars, dwFillAttribute, dwFlags;\n"
+                 "    unsigned short wShowWindow, cbReserved2;\n"
+                 "    char *lpReserved2;\n"
+                 "    void *hStdInput, *hStdOutput, *hStdError;\n"
+                 "} STARTUPINFOA;\n"
                  "int _ARGC;\n"
                  "WCHAR **_ARGV;\n"
-                 "extern int __stdcall %s(HINSTANCE,HINSTANCE,LPSTR,INT);\n"
+                 "extern int __stdcall %s(void *,void *,char *,int);\n"
+                 "extern char * __stdcall GetCommandLineA(void);\n"
+                 "extern void * __stdcall GetModuleHandleA(char *);\n"
+                 "extern void __stdcall GetStartupInfoA(STARTUPINFOA *);\n"
+                 "extern void __stdcall ExitProcess(unsigned int);\n"
                  "static void __wine_exe_main(void)\n"
                  "{\n"
                  "    extern int __wine_get_wmain_args( WCHAR ***argv );\n"
                  "    STARTUPINFOA info;\n"
-                 "    LPSTR cmdline = GetCommandLineA();\n"
+                 "    char *cmdline = GetCommandLineA();\n"
                  "    while (*cmdline && *cmdline != ' ') cmdline++;\n"
                  "    if (*cmdline) cmdline++;\n"
                  "    GetStartupInfoA( &info );\n"
-                 "    if (!(info.dwFlags & STARTF_USESHOWWINDOW)) info.wShowWindow = 1;\n"
+                 "    if (!(info.dwFlags & 1)) info.wShowWindow = 1;\n"
                  "    _ARGC = __wine_get_wmain_args( &_ARGV );\n"
                  "    ExitProcess( %s( GetModuleHandleA(0), 0, cmdline, info.wShowWindow ) );\n"
                  "}\n\n", init_func, init_func );