diff --git a/dlls/crypt32/tests/msg.c b/dlls/crypt32/tests/msg.c
index 3bd0882102b..f65c7f8f2b3 100644
--- a/dlls/crypt32/tests/msg.c
+++ b/dlls/crypt32/tests/msg.c
@@ -1853,6 +1853,7 @@ static void test_decode_msg_get_param(void)
     HCRYPTMSG msg;
     BOOL ret;
     DWORD size = 0, version;
+    LPBYTE buf;
 
     msg = CryptMsgOpenToDecode(PKCS_7_ASN_ENCODING, 0, 0, 0, NULL, NULL);
     SetLastError(0xdeadbeef);
@@ -1879,7 +1880,19 @@ static void test_decode_msg_get_param(void)
      sizeof(hashParam));
     check_param("hash computed hash", msg, CMSG_COMPUTED_HASH_PARAM,
      hashParam, sizeof(hashParam));
-    size = strlen(szOID_RSA_data) + 1;
+    /* Curiously, getting the hash of index 1 succeeds, even though there's
+     * only one hash.
+     */
+    ret = CryptMsgGetParam(msg, CMSG_COMPUTED_HASH_PARAM, 1, NULL, &size);
+    ok(ret, "CryptMsgGetParam failed: %08x\n", GetLastError());
+    buf = CryptMemAlloc(size);
+    if (buf)
+    {
+        ret = CryptMsgGetParam(msg, CMSG_COMPUTED_HASH_PARAM, 1, buf, &size);
+        ok(size == sizeof(hashParam), "Unexpected size %d\n", size);
+        ok(!memcmp(buf, hashParam, size), "Unexpected value\n");
+        CryptMemFree(buf);
+    }
     check_param("hash inner OID", msg, CMSG_INNER_CONTENT_TYPE_PARAM,
      (const BYTE *)szOID_RSA_data, strlen(szOID_RSA_data) + 1);
     version = CMSG_HASHED_DATA_V0;