diff --git a/dlls/crypt32/sip.c b/dlls/crypt32/sip.c
index 4a32cada900..8b561fdc2c7 100644
--- a/dlls/crypt32/sip.c
+++ b/dlls/crypt32/sip.c
@@ -210,7 +210,7 @@ BOOL WINAPI CryptSIPAddProvider(SIP_ADD_NEWPROVIDER *psNewProv)
     TRACE("%p\n", psNewProv);
 
     if (!psNewProv ||
-        psNewProv->cbStruct != sizeof(SIP_ADD_NEWPROVIDER) ||
+        psNewProv->cbStruct < FIELD_OFFSET(SIP_ADD_NEWPROVIDER, pwszGetCapFuncName) ||
         !psNewProv->pwszGetFuncName ||
         !psNewProv->pwszPutFuncName ||
         !psNewProv->pwszCreateFuncName ||
diff --git a/dlls/msisip/main.c b/dlls/msisip/main.c
index 0b4d2c3cc9a..882db3d9d84 100644
--- a/dlls/msisip/main.c
+++ b/dlls/msisip/main.c
@@ -81,6 +81,7 @@ HRESULT WINAPI DllRegisterServer(void)
     prov.pwszVerifyFuncName = verifyIndirectData;
     prov.pwszRemoveFuncName = removeSignedDataMsg;
     prov.pwszIsFunctionNameFmt2 = isMyTypeOfFile;
+    prov.pwszGetCapFuncName = NULL;
     return CryptSIPAddProvider(&prov) ? S_OK : S_FALSE;
 }
 
diff --git a/dlls/wintrust/register.c b/dlls/wintrust/register.c
index f039fbdcab6..9981fbccb47 100644
--- a/dlls/wintrust/register.c
+++ b/dlls/wintrust/register.c
@@ -911,6 +911,7 @@ static BOOL WINTRUST_SIPPAddProvider(GUID* Subject, WCHAR* MagicNumber)
     NewProv.pwszVerifyFuncName     = CryptSIPVerifyIndirectData;
     NewProv.pwszRemoveFuncName     = CryptSIPRemoveSignedDataMsg;
     NewProv.pwszIsFunctionNameFmt2 = NULL;
+    NewProv.pwszGetCapFuncName     = NULL;
 
     Ret = CryptSIPAddProvider(&NewProv);
 
diff --git a/include/mssip.h b/include/mssip.h
index b0b21a60a7f..c14f02de5f8 100644
--- a/include/mssip.h
+++ b/include/mssip.h
@@ -156,6 +156,9 @@ typedef struct SIP_ADD_NEWPROVIDER_
   WCHAR *pwszRemoveFuncName;
 
   WCHAR *pwszIsFunctionNameFmt2;
+
+  /* NTDDI_VERSION >= NTDDI_WIN8 */
+  WCHAR *pwszGetCapFuncName;
 } SIP_ADD_NEWPROVIDER, *PSIP_ADD_NEWPROVIDER;
 #include <poppack.h>