diff --git a/dlls/msvcp90/memory.c b/dlls/msvcp90/memory.c
index c5cae500196..5d439101a51 100644
--- a/dlls/msvcp90/memory.c
+++ b/dlls/msvcp90/memory.c
@@ -111,7 +111,7 @@ void __thiscall MSVCP_allocator_char_destroy(void *this, char *ptr)
 /* ?max_size@?$allocator@D@std@@QBEIXZ */
 /* ?max_size@?$allocator@D@std@@QEBA_KXZ */
 DEFINE_THISCALL_WRAPPER(MSVCP_allocator_char_max_size, 4)
-MSVCP_size_t __thiscall MSVCP_allocator_char_max_size(void *this)
+MSVCP_size_t __thiscall MSVCP_allocator_char_max_size(const void *this)
 {
     return UINT_MAX/sizeof(char);
 }
@@ -208,7 +208,7 @@ void __thiscall MSVCP_allocator_wchar_destroy(void *this, char *ptr)
 /* ?max_size@?$allocator@_W@std@@QBEIXZ */
 /* ?max_size@?$allocator@_W@std@@QEBA_KXZ */
 DEFINE_THISCALL_WRAPPER(MSVCP_allocator_wchar_max_size, 4)
-MSVCP_size_t __thiscall MSVCP_allocator_wchar_max_size(void *this)
+MSVCP_size_t __thiscall MSVCP_allocator_wchar_max_size(const void *this)
 {
     return UINT_MAX/sizeof(wchar_t);
 }
diff --git a/dlls/msvcp90/msvcp90.h b/dlls/msvcp90/msvcp90.h
index 3fb67900343..0a60d469c88 100644
--- a/dlls/msvcp90/msvcp90.h
+++ b/dlls/msvcp90/msvcp90.h
@@ -74,13 +74,18 @@ extern MSVCP_bool (__thiscall *critical_section_trylock)(critical_section*);
 #define BUF_SIZE_CHAR 16
 typedef struct
 {
+#if _MSVCP_VER <= 90
     void *allocator;
+#endif
     union {
         char buf[BUF_SIZE_CHAR];
         char *ptr;
     } data;
     MSVCP_size_t size;
     MSVCP_size_t res;
+#if _MSVCP_VER == 100
+    char allocator;
+#endif
 } basic_string_char;
 
 basic_string_char* __thiscall MSVCP_basic_string_char_ctor(basic_string_char*);
@@ -97,13 +102,18 @@ basic_string_char* __thiscall MSVCP_basic_string_char_assign(basic_string_char*,
 #define BUF_SIZE_WCHAR 8
 typedef struct
 {
+#if _MSVCP_VER <= 90
     void *allocator;
+#endif
     union {
         wchar_t buf[BUF_SIZE_WCHAR];
         wchar_t *ptr;
     } data;
     MSVCP_size_t size;
     MSVCP_size_t res;
+#if _MSVCP_VER == 100
+    char allocator;
+#endif
 } basic_string_wchar;
 
 basic_string_wchar* __thiscall MSVCP_basic_string_wchar_ctor(basic_string_wchar*);
@@ -117,10 +127,10 @@ MSVCP_size_t __thiscall MSVCP_basic_string_wchar_length(const basic_string_wchar
 
 char* __thiscall MSVCP_allocator_char_allocate(void*, MSVCP_size_t);
 void __thiscall MSVCP_allocator_char_deallocate(void*, char*, MSVCP_size_t);
-MSVCP_size_t __thiscall MSVCP_allocator_char_max_size(void*);
+MSVCP_size_t __thiscall MSVCP_allocator_char_max_size(const void*);
 wchar_t* __thiscall MSVCP_allocator_wchar_allocate(void*, MSVCP_size_t);
 void __thiscall MSVCP_allocator_wchar_deallocate(void*, wchar_t*, MSVCP_size_t);
-MSVCP_size_t __thiscall MSVCP_allocator_wchar_max_size(void*);
+MSVCP_size_t __thiscall MSVCP_allocator_wchar_max_size(const void*);
 
 typedef struct
 {
diff --git a/dlls/msvcp90/string.c b/dlls/msvcp90/string.c
index ce056136533..810fb5af129 100644
--- a/dlls/msvcp90/string.c
+++ b/dlls/msvcp90/string.c
@@ -29,6 +29,14 @@
 #include "wine/debug.h"
 WINE_DEFAULT_DEBUG_CHANNEL(msvcp);
 
+#if _MSVCP_VER <= 90
+#define STRING_ALLOCATOR(this) ((this)->allocator)
+#elif _MSVCP_VER == 100
+#define STRING_ALLOCATOR(this) (&(this)->allocator)
+#else
+#define STRING_ALLOCATOR(this) NULL
+#endif
+
 /* size_t_noverify structure */
 typedef struct {
     MSVCP_size_t val;
@@ -546,7 +554,7 @@ void __thiscall basic_string_char_tidy(basic_string_char *this,
 
         if(new_size > 0)
             MSVCP_char_traits_char__Copy_s(this->data.buf, BUF_SIZE_CHAR, ptr, new_size);
-        MSVCP_allocator_char_deallocate(this->allocator, ptr, this->res+1);
+        MSVCP_allocator_char_deallocate(STRING_ALLOCATOR(this), ptr, this->res+1);
     }
 
     this->res = BUF_SIZE_CHAR-1;
@@ -577,9 +585,9 @@ MSVCP_bool __thiscall basic_string_char_grow(
         if(new_res/3 < this->res/2)
             new_res = this->res + this->res/2;
 
-        ptr = MSVCP_allocator_char_allocate(this->allocator, new_res+1);
+        ptr = MSVCP_allocator_char_allocate(STRING_ALLOCATOR(this), new_res+1);
         if(!ptr)
-            ptr = MSVCP_allocator_char_allocate(this->allocator, new_size+1);
+            ptr = MSVCP_allocator_char_allocate(STRING_ALLOCATOR(this), new_size+1);
         else
             new_size = new_res;
         if(!ptr) {
@@ -988,7 +996,7 @@ DEFINE_THISCALL_WRAPPER(basic_string_char_max_size, 4)
 MSVCP_size_t __thiscall basic_string_char_max_size(const basic_string_char *this)
 {
     TRACE("%p\n", this);
-    return MSVCP_allocator_char_max_size(this->allocator)-1;
+    return MSVCP_allocator_char_max_size(STRING_ALLOCATOR(this))-1;
 }
 
 /* ?empty@?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@QBE_NXZ */
@@ -2228,7 +2236,7 @@ void __thiscall basic_string_wchar_tidy(basic_string_wchar *this,
 
         if(new_size > 0)
             MSVCP_char_traits_wchar__Copy_s(this->data.buf, BUF_SIZE_WCHAR, ptr, new_size);
-        MSVCP_allocator_wchar_deallocate(this->allocator, ptr, this->res+1);
+        MSVCP_allocator_wchar_deallocate(STRING_ALLOCATOR(this), ptr, this->res+1);
     }
 
     this->res = BUF_SIZE_WCHAR-1;
@@ -2252,9 +2260,9 @@ MSVCP_bool __thiscall basic_string_wchar_grow(
         if(new_res/3 < this->res/2)
             new_res = this->res + this->res/2;
 
-        ptr = MSVCP_allocator_wchar_allocate(this->allocator, new_res+1);
+        ptr = MSVCP_allocator_wchar_allocate(STRING_ALLOCATOR(this), new_res+1);
         if(!ptr)
-            ptr = MSVCP_allocator_wchar_allocate(this->allocator, new_size+1);
+            ptr = MSVCP_allocator_wchar_allocate(STRING_ALLOCATOR(this), new_size+1);
         else
             new_size = new_res;
         if(!ptr) {
@@ -2733,7 +2741,7 @@ DEFINE_THISCALL_WRAPPER(basic_string_wchar_max_size, 4)
 MSVCP_size_t __thiscall basic_string_wchar_max_size(const basic_string_wchar *this)
 {
     TRACE("%p\n", this);
-    return MSVCP_allocator_wchar_max_size(this->allocator)-1;
+    return MSVCP_allocator_wchar_max_size(STRING_ALLOCATOR(this))-1;
 }
 
 /* ?empty@?$basic_string@_WU?$char_traits@_W@std@@V?$allocator@_W@2@@std@@QBE_NXZ */