diff --git a/dlls/crypt32/decode.c b/dlls/crypt32/decode.c
index cda8b62aed1..2c2b543e852 100644
--- a/dlls/crypt32/decode.c
+++ b/dlls/crypt32/decode.c
@@ -1724,9 +1724,8 @@ static BOOL CRYPT_AsnDecodeUnicodeNameValueInternal(const BYTE *pbEncoded,
                 case ASN_UTF8STRING:
                     value->Value.cbData = MultiByteToWideChar(CP_UTF8, 0,
                      (LPCSTR)pbEncoded + 1 + lenBytes, dataLen,
-                     str, bytesNeeded - sizeof(CERT_NAME_VALUE)) * 2;
-                    value->Value.pbData[value->Value.cbData / sizeof(WCHAR)]
-                     = 0;
+                     str, bytesNeeded - sizeof(CERT_NAME_VALUE)) * sizeof(WCHAR);
+                    *(WCHAR *)(value->Value.pbData + value->Value.cbData) = 0;
                     value->Value.cbData += sizeof(WCHAR);
                     break;
                 }