diff --git a/dlls/crypt32/main.c b/dlls/crypt32/main.c
index dd9e1fbbda5..f5d68d55f88 100644
--- a/dlls/crypt32/main.c
+++ b/dlls/crypt32/main.c
@@ -238,5 +238,7 @@ BOOL WINAPI CryptVerifyMessageSignature(PCRYPT_VERIFY_MESSAGE_PARA pVerifyPara,
     FIXME("stub: %p, %d, %p, %d, %p, %p, %p\n",
         pVerifyPara, dwSignerIndex, pbSignedBlob, cbSignedBlob,
         pbDecoded, pcbDecoded, ppSignerCert);
+    if (ppSignerCert)
+        *ppSignerCert = NULL;
     return FALSE;
 }