diff --git a/dlls/advapi32/crypt.c b/dlls/advapi32/crypt.c
index cae03d8f6bf..d1fc25de528 100644
--- a/dlls/advapi32/crypt.c
+++ b/dlls/advapi32/crypt.c
@@ -2243,7 +2243,7 @@ BOOL WINAPI CryptVerifySignatureA (HCRYPTHASH hHash, CONST BYTE *pbSignature, DW
  *  TRUE  if blocks are the same
  *  FALSE if blocks are different
  */
-BOOL WINAPI SystemFunction030(PVOID b1, PVOID b2)
+BOOL WINAPI SystemFunction030(LPCVOID b1, LPCVOID b2)
 {
     return !memcmp(b1, b2, 0x10);
 }
diff --git a/dlls/advapi32/crypt.h b/dlls/advapi32/crypt.h
index 3d630da0bcf..d9018f4c642 100644
--- a/dlls/advapi32/crypt.h
+++ b/dlls/advapi32/crypt.h
@@ -93,6 +93,6 @@ struct ustring {
     unsigned char *Buffer;
 };
 
-NTSTATUS WINAPI SystemFunction032(struct ustring *data, struct ustring *key);
+NTSTATUS WINAPI SystemFunction032(struct ustring *data, const struct ustring *key);
 
 #endif /* __WINE_CRYPT_H_ */
diff --git a/dlls/advapi32/crypt_arc4.c b/dlls/advapi32/crypt_arc4.c
index ebe4058794b..523cda224e7 100644
--- a/dlls/advapi32/crypt_arc4.c
+++ b/dlls/advapi32/crypt_arc4.c
@@ -94,7 +94,7 @@ static void arc4_ProcessString(arc4_info *a4i, BYTE *inoutString, unsigned int l
  * NOTES
  *  see http://web.it.kth.se/~rom/ntsec.html#crypto-strongavail
  */
-NTSTATUS WINAPI SystemFunction032(struct ustring *data, struct ustring *key)
+NTSTATUS WINAPI SystemFunction032(struct ustring *data, const struct ustring *key)
 {
     arc4_info a4i;
 
diff --git a/dlls/advapi32/tests/crypt_lmhash.c b/dlls/advapi32/tests/crypt_lmhash.c
index 66ebe829578..253090a970e 100644
--- a/dlls/advapi32/tests/crypt_lmhash.c
+++ b/dlls/advapi32/tests/crypt_lmhash.c
@@ -43,8 +43,8 @@ typedef VOID (WINAPI *fnSystemFunction006)( PCSTR passwd, PSTR lmhash );
 typedef NTSTATUS (WINAPI *fnSystemFunction008)(const BYTE *, const BYTE *, LPBYTE);
 typedef NTSTATUS (WINAPI *fnSystemFunction009)(const BYTE *, const BYTE *, LPBYTE);
 typedef int (WINAPI *descrypt)(unsigned char *, unsigned char *, unsigned char *);
-typedef NTSTATUS (WINAPI *fnSystemFunction030)(void*, void*);
-typedef NTSTATUS (WINAPI *fnSystemFunction032)(struct ustring *, struct ustring *);
+typedef NTSTATUS (WINAPI *fnSystemFunction030)(const void*, const void*);
+typedef NTSTATUS (WINAPI *fnSystemFunction032)(struct ustring *, const struct ustring *);
 
 fnSystemFunction001 pSystemFunction001;
 fnSystemFunction002 pSystemFunction002;