diff --git a/include/msvcrt/corecrt_wctype.h b/include/msvcrt/corecrt_wctype.h
index b9929383d03..af44e86772b 100644
--- a/include/msvcrt/corecrt_wctype.h
+++ b/include/msvcrt/corecrt_wctype.h
@@ -24,6 +24,8 @@ extern "C" {
 #define _LEADBYTE     0x8000
 #define _ALPHA       (0x0100|_UPPER|_LOWER)  /* (C1_ALPHA|_UPPER|_LOWER) */
 
+int     __cdecl _iswblank_l(wint_t,_locale_t);
+int     __cdecl _iswctype_l(wint_t,wctype_t,_locale_t);
 wchar_t __cdecl _towlower_l(wchar_t,_locale_t);
 wchar_t __cdecl _towupper_l(wchar_t,_locale_t);
 int     __cdecl is_wctype(wint_t,wctype_t);
@@ -31,6 +33,7 @@ int     __cdecl isleadbyte(int);
 int     __cdecl iswalnum(wint_t);
 int     __cdecl iswalpha(wint_t);
 int     __cdecl iswascii(wint_t);
+int     __cdecl iswblank(wint_t);
 int     __cdecl iswcntrl(wint_t);
 int     __cdecl iswctype(wint_t,wctype_t);
 int     __cdecl iswdigit(wint_t);
diff --git a/include/msvcrt/ctype.h b/include/msvcrt/ctype.h
index 6b6cf07cd96..872afb3e740 100644
--- a/include/msvcrt/ctype.h
+++ b/include/msvcrt/ctype.h
@@ -22,6 +22,7 @@ int __cdecl __isascii(int);
 int __cdecl __iscsym(int);
 int __cdecl __iscsymf(int);
 int __cdecl __toascii(int);
+int __cdecl _isblank_l(int,_locale_t);
 int __cdecl _isctype(int,int);
 int __cdecl _tolower(int);
 int __cdecl _tolower_l(int,_locale_t);
@@ -29,6 +30,7 @@ int __cdecl _toupper(int);
 int __cdecl _toupper_l(int,_locale_t);
 int __cdecl isalnum(int);
 int __cdecl isalpha(int);
+int __cdecl isblank(int);
 int __cdecl iscntrl(int);
 int __cdecl isdigit(int);
 int __cdecl isgraph(int);