diff --git a/reactos/dll/win32/msvcrt/msvcrt.spec b/reactos/dll/win32/msvcrt/msvcrt.spec
index 4c3131bac9b..9e23b5ce679 100644
--- a/reactos/dll/win32/msvcrt/msvcrt.spec
+++ b/reactos/dll/win32/msvcrt/msvcrt.spec
@@ -156,7 +156,7 @@
 @ cdecl __isascii(long)
 @ cdecl __iscsym(long)
 @ cdecl __iscsymf(long)
-@ extern __lc_codepage MSVCRT___lc_codepage
+@ extern __lc_codepage
 # @ stub __lc_collate # not in XP / 7
 @ extern __lc_collate_cp MSVCRT___lc_collate_cp
 @ extern __lc_handle MSVCRT___lc_handle
diff --git a/reactos/lib/sdk/crt/include/internal/mbstring.h b/reactos/lib/sdk/crt/include/internal/mbstring.h
index 8ceb83fa921..bf81b5d640f 100644
--- a/reactos/lib/sdk/crt/include/internal/mbstring.h
+++ b/reactos/lib/sdk/crt/include/internal/mbstring.h
@@ -39,7 +39,6 @@
 
 #define MAX_LOCALE_LENGTH 256
 extern unsigned char _mbctype[257];
-extern unsigned int MSVCRT___lc_codepage;
 extern char MSVCRT_current_lc_all[MAX_LOCALE_LENGTH];
 
 #if defined (_MSC_VER)
diff --git a/reactos/lib/sdk/crt/include/internal/wine/msvcrt.h b/reactos/lib/sdk/crt/include/internal/wine/msvcrt.h
index 4c15a17e8a9..c771f83d134 100644
--- a/reactos/lib/sdk/crt/include/internal/wine/msvcrt.h
+++ b/reactos/lib/sdk/crt/include/internal/wine/msvcrt.h
@@ -25,7 +25,7 @@
 #include "windef.h"
 #include "winbase.h"
 
-extern int __lc_codepage;
+extern unsigned int __lc_codepage;
 extern int __lc_collate_cp;
 extern int __mb_cur_max;
 extern const unsigned short _ctype [257];
diff --git a/reactos/lib/sdk/crt/locale/locale.c b/reactos/lib/sdk/crt/locale/locale.c
index 1c7f76fb889..557b99c24e0 100644
--- a/reactos/lib/sdk/crt/locale/locale.c
+++ b/reactos/lib/sdk/crt/locale/locale.c
@@ -31,7 +31,7 @@
 #error _pctype should not be defined
 #endif
 
-unsigned int MSVCRT___lc_codepage = 0;
+unsigned int __lc_codepage = 0;
 int MSVCRT___lc_collate_cp = 0;
 LCID MSVCRT___lc_handle[LC_MAX - LC_MIN + 1] = { 0 };
 int __mb_cur_max = 1;
@@ -622,7 +622,7 @@ LCID* CDECL ___lc_handle_func(void)
  */
 unsigned int CDECL ___lc_codepage_func(void)
 {
-    return MSVCRT___lc_codepage;
+    return __lc_codepage;
 }
 
 /*********************************************************************
@@ -1391,7 +1391,7 @@ char* CDECL setlocale(int category, const char* locale)
     if(locinfo == MSVCRT_locale->locinfo) {
         int i;
 
-        MSVCRT___lc_codepage = locinfo->lc_codepage;
+        __lc_codepage = locinfo->lc_codepage;
         MSVCRT___lc_collate_cp = locinfo->lc_collate_cp;
         __mb_cur_max = locinfo->mb_cur_max;
         _pctype = locinfo->pctype;
@@ -1488,7 +1488,7 @@ void __init_global_locale()
         return;
     global_locale = MSVCRT__create_locale(0, "C");
     
-    MSVCRT___lc_codepage = MSVCRT_locale->locinfo->lc_codepage;
+    __lc_codepage = MSVCRT_locale->locinfo->lc_codepage;
     MSVCRT___lc_collate_cp = MSVCRT_locale->locinfo->lc_collate_cp;
     __mb_cur_max = MSVCRT_locale->locinfo->mb_cur_max;
     for(i=LC_MIN; i<=LC_MAX; i++)
diff --git a/reactos/lib/sdk/crt/mbstring/jistojms.c b/reactos/lib/sdk/crt/mbstring/jistojms.c
index 76a2424467f..d4835855bdf 100644
--- a/reactos/lib/sdk/crt/mbstring/jistojms.c
+++ b/reactos/lib/sdk/crt/mbstring/jistojms.c
@@ -33,7 +33,7 @@ unsigned int _mbcjistojms(unsigned int c)
 {
  /* Conversion takes place only when codepage is 932.
      In all other cases, c is returned unchanged */
-  if(MSVCRT___lc_codepage == 932)
+  if(get_mbcinfo()->mbcodepage == 932)
   {
     if(HIBYTE(c) >= 0x21 && HIBYTE(c) <= 0x7e &&
        LOBYTE(c) >= 0x21 && LOBYTE(c) <= 0x7e)
@@ -43,7 +43,7 @@ unsigned int _mbcjistojms(unsigned int c)
       else
         c += 0x7d;
 
-      if(LOBYTE(c) > 0x7F)
+      if(LOBYTE(c) >= 0x7F)
         c += 0x1;
 
       c = (((HIBYTE(c) - 0x21)/2 + 0x81) << 8) | LOBYTE(c);
diff --git a/reactos/lib/sdk/crt/mbstring/jmstojis.c b/reactos/lib/sdk/crt/mbstring/jmstojis.c
index 8e634c3e67d..97225453749 100644
--- a/reactos/lib/sdk/crt/mbstring/jmstojis.c
+++ b/reactos/lib/sdk/crt/mbstring/jmstojis.c
@@ -1,28 +1,34 @@
+#include <precomp.h>
 #include <mbstring.h>
+#include <locale.h>
 
 /*
  * @implemented
  */
-unsigned int _mbcjmstojis(unsigned int c)
+unsigned int __cdecl _mbcjmstojis(unsigned int c)
 {
-  int c1, c2;
+  /* Conversion takes place only when codepage is 932.
+     In all other cases, c is returned unchanged */
+  if(get_mbcinfo()->mbcodepage == 932)
+  {
+    if(_ismbclegal(c) && HIBYTE(c) < 0xf0)
+    {
+      if(HIBYTE(c) >= 0xe0)
+        c -= 0x4000;
 
-  c2 = (unsigned char)c;
-  c1 = c >> 8;
-  if (c1 < 0xf0 && _ismbblead(c1) && _ismbbtrail(c2)) {
-    if (c1 >= 0xe0)
-      c1 -= 0x40;
-    c1 -= 0x70;
-    c1 <<= 1;
-    if (c2 < 0x9f) {
-      c1 --;
-      c2 -= 0x1f;
-      if (c2 >= (0x80-0x1f))
-        c2 --;
-    } else {
-      c2 -= 0x7e;
+      c = (((HIBYTE(c) - 0x81)*2 + 0x21) << 8) | LOBYTE(c);
+
+      if(LOBYTE(c) > 0x7f)
+        c -= 0x1;
+
+      if(LOBYTE(c) > 0x9d)
+        c += 0x83;
+      else
+        c -= 0x1f;
     }
-    return ((c1 << 8) | c2);
+    else
+      return 0; /* Codepage is 932, but c can't be converted */
   }
-  return 0;
+
+  return c;
 }