diff --git a/Source/appfat.cpp b/Source/appfat.cpp
index 6844f61c8..e5d8d8e23 100644
--- a/Source/appfat.cpp
+++ b/Source/appfat.cpp
@@ -332,7 +332,7 @@ void __fastcall ErrDlg(int template_id, int error_code, char *log_file_path, int
 	TermMsg(0);
 }
 
-bool __stdcall FuncDlg(HWND hDlg, UINT uMsg, WPARAM wParam, char *text)
+BOOL __stdcall FuncDlg(HWND hDlg, UINT uMsg, WPARAM wParam, char *text)
 {
 	if ( uMsg == WM_INITDIALOG )
 	{
diff --git a/Source/appfat.h b/Source/appfat.h
index eb98e830c..5d9b40db8 100644
--- a/Source/appfat.h
+++ b/Source/appfat.h
@@ -19,7 +19,7 @@ void __fastcall DDErrMsg(int error_code, int log_line_nr, char *log_file_path);
 void __fastcall DSErrMsg(int error_code, int log_line_nr, char *log_file_path);
 void __fastcall center_window(HWND hDlg);
 void __fastcall ErrDlg(int template_id, int error_code, char *log_file_path, int log_line_nr);
-bool __stdcall FuncDlg(HWND hDlg, UINT uMsg, WPARAM wParam, char *text);
+BOOL __stdcall FuncDlg(HWND hDlg, UINT uMsg, WPARAM wParam, char *text);
 void __fastcall TextDlg(HWND hDlg, char *text);
 void __fastcall ErrOkDlg(int template_id, int error_code, char *log_file_path, int log_line_nr);
 void __fastcall FileErrDlg(char *error);