diff --git a/reactos/include/crt/ctype.h b/reactos/include/crt/ctype.h
index a997504c288..24f5877bd1b 100644
--- a/reactos/include/crt/ctype.h
+++ b/reactos/include/crt/ctype.h
@@ -112,9 +112,9 @@ _CRTIMP int __cdecl __MINGW_NOTHROW _toupper(int);
   __MINGW_IMPORT unsigned short _ctype[];
 # endif
 # ifdef __MSVCRT__
-  __MINGW_IMPORT unsigned short* _pctype;
+  __MINGW_IMPORT const unsigned short* _pctype;
 # else /* CRTDLL */
-  __MINGW_IMPORT unsigned short* _pctype_dll;
+  __MINGW_IMPORT const unsigned short* _pctype_dll;
 # define  _pctype _pctype_dll
 # endif 
 
diff --git a/reactos/include/crt/wctype.h b/reactos/include/crt/wctype.h
index 5e2dc88b83c..ec342231f8c 100644
--- a/reactos/include/crt/wctype.h
+++ b/reactos/include/crt/wctype.h
@@ -99,9 +99,9 @@ _CRTIMP int __cdecl __MINGW_NOTHROW	isleadbyte (int);
   __MINGW_IMPORT unsigned short _ctype[];
 # endif 
 # ifdef __MSVCRT__
-  __MINGW_IMPORT unsigned short* _pctype;
+  __MINGW_IMPORT const unsigned short* _pctype;
 # else	/* CRTDLL */
-  __MINGW_IMPORT unsigned short* _pctype_dll;
+  __MINGW_IMPORT const unsigned short* _pctype_dll;
 # define  _pctype _pctype_dll
 # endif
 
diff --git a/reactos/lib/sdk/crt/string/ctype.c b/reactos/lib/sdk/crt/string/ctype.c
index c9a542f185e..5c5f4549b33 100644
--- a/reactos/lib/sdk/crt/string/ctype.c
+++ b/reactos/lib/sdk/crt/string/ctype.c
@@ -266,13 +266,13 @@ unsigned short _ctype[] = {
 	0			/* 0xff */
 };
 
-unsigned short *_pctype = _ctype + 1;
-unsigned short *_pwctype = _ctype + 1;
+const unsigned short *_pctype = _ctype + 1;
+const unsigned short *_pwctype = _ctype + 1;
 
 /*
  * @implemented
  */
-unsigned short **__p__pctype(void)
+const unsigned short **__p__pctype(void)
 {
    return &_pctype;
 }
@@ -280,7 +280,7 @@ unsigned short **__p__pctype(void)
 /*
  * @implemented
  */
-unsigned short **__p__pwctype(void)
+const unsigned short **__p__pwctype(void)
 {
    return &_pwctype;
 }