diff --git a/dlls/ntdll/rtl.c b/dlls/ntdll/rtl.c
index 21866ef366a..3ff5cb040a7 100644
--- a/dlls/ntdll/rtl.c
+++ b/dlls/ntdll/rtl.c
@@ -583,7 +583,7 @@ VOID WINAPI RtlFillMemoryUlong(ULONG* lpDest, ULONG ulCount, ULONG ulValue)
  * RETURNS
  *  The cumulative CRC32 of dwInitial and iLen bytes of the pData block.
  */
-DWORD WINAPI RtlComputeCrc32(DWORD dwInitial, PBYTE pData, INT iLen)
+DWORD WINAPI RtlComputeCrc32(DWORD dwInitial, const BYTE *pData, INT iLen)
 {
   DWORD crc = ~dwInitial;
 
diff --git a/dlls/ntdll/tests/rtl.c b/dlls/ntdll/tests/rtl.c
index 8d7f227d6a1..8a5611c4e10 100644
--- a/dlls/ntdll/tests/rtl.c
+++ b/dlls/ntdll/tests/rtl.c
@@ -844,7 +844,7 @@ static void test_RtlComputeCrc32(void)
   if (!pRtlComputeCrc32)
     return;
 
-  crc = pRtlComputeCrc32(crc, (LPBYTE)src, LEN);
+  crc = pRtlComputeCrc32(crc, (const BYTE *)src, LEN);
   ok(crc == 0x40861dc2,"Expected 0x40861dc2, got %8x\n", crc);
 }
 
diff --git a/include/winternl.h b/include/winternl.h
index 95091768f92..19b2ac94327 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -1986,7 +1986,7 @@ PDEBUG_BUFFER WINAPI RtlCreateQueryDebugBuffer(ULONG,BOOLEAN);
 ULONG     WINAPI RtlCompactHeap(HANDLE,ULONG);
 LONG      WINAPI RtlCompareString(const STRING*,const STRING*,BOOLEAN);
 LONG      WINAPI RtlCompareUnicodeString(const UNICODE_STRING*,const UNICODE_STRING*,BOOLEAN);
-DWORD     WINAPI RtlComputeCrc32(DWORD,PBYTE,INT);
+DWORD     WINAPI RtlComputeCrc32(DWORD,const BYTE*,INT);
 NTSTATUS  WINAPI RtlConvertSidToUnicodeString(PUNICODE_STRING,PSID,BOOLEAN);
 LONGLONG  WINAPI RtlConvertLongToLargeInteger(LONG);
 ULONGLONG WINAPI RtlConvertUlongToLargeInteger(ULONG);