diff --git a/dlls/crypt32/decode.c b/dlls/crypt32/decode.c
index 6370d812dc2..78bc365db1b 100644
--- a/dlls/crypt32/decode.c
+++ b/dlls/crypt32/decode.c
@@ -1836,6 +1836,8 @@ static BOOL CRYPT_AsnDecodeCopyBytesInternal(const BYTE *pbEncoded,
             assert(blob->pbData);
             memcpy(blob->pbData, pbEncoded, blob->cbData);
         }
+        if (pcbDecoded)
+            *pcbDecoded = cbEncoded;
     }
     return ret;
 }