diff --git a/dlls/ntdll/env.c b/dlls/ntdll/env.c
index 193237dab78..fd6f1850017 100644
--- a/dlls/ntdll/env.c
+++ b/dlls/ntdll/env.c
@@ -263,7 +263,7 @@ done:
  *		RtlExpandEnvironmentStrings_U (NTDLL.@)
  *
  */
-NTSTATUS WINAPI RtlExpandEnvironmentStrings_U(PWSTR renv, const UNICODE_STRING* us_src,
+NTSTATUS WINAPI RtlExpandEnvironmentStrings_U(PCWSTR renv, const UNICODE_STRING* us_src,
                                               PUNICODE_STRING us_dst, PULONG plen)
 {
     DWORD src_len, len, count, total_size = 1;  /* 1 for terminating '\0' */
@@ -367,9 +367,9 @@ PRTL_USER_PROCESS_PARAMETERS WINAPI RtlNormalizeProcessParams( RTL_USER_PROCESS_
 }
 
 
-static inline void denormalize( void *base, WCHAR **ptr )
+static inline void denormalize( const void *base, WCHAR **ptr )
 {
-    if (*ptr) *ptr = (WCHAR *)(UINT_PTR)((char *)*ptr - (char *)base);
+    if (*ptr) *ptr = (WCHAR *)(UINT_PTR)((char *)*ptr - (const char *)base);
 }
 
 /******************************************************************************
diff --git a/include/winternl.h b/include/winternl.h
index afbf47bd774..9226d144d14 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -2057,7 +2057,7 @@ BOOL      WINAPI RtlEqualSid(PSID,PSID);
 BOOLEAN   WINAPI RtlEqualString(const STRING*,const STRING*,BOOLEAN);
 BOOLEAN   WINAPI RtlEqualUnicodeString(const UNICODE_STRING*,const UNICODE_STRING*,BOOLEAN);
 void      DECLSPEC_NORETURN WINAPI RtlExitUserThread(ULONG);
-NTSTATUS  WINAPI RtlExpandEnvironmentStrings_U(PWSTR, const UNICODE_STRING*, UNICODE_STRING*, ULONG*);
+NTSTATUS  WINAPI RtlExpandEnvironmentStrings_U(PCWSTR, const UNICODE_STRING*, UNICODE_STRING*, ULONG*);
 LONGLONG  WINAPI RtlExtendedMagicDivide(LONGLONG,LONGLONG,INT);
 LONGLONG  WINAPI RtlExtendedIntegerMultiply(LONGLONG,INT);
 LONGLONG  WINAPI RtlExtendedLargeIntegerDivide(LONGLONG,INT,INT *);