diff --git a/src/cryptojwt/jwe/__init__.py b/src/cryptojwt/jwe/__init__.py
index f0e511bb..ffddcf13 100644
--- a/src/cryptojwt/jwe/__init__.py
+++ b/src/cryptojwt/jwe/__init__.py
@@ -32,6 +32,11 @@
     ],
 }
 
+DEPRECATED = {
+    "alg": ["RSA1_5"],
+    "enc": [],
+}
+
 
 class Encrypter(object):
     """Abstract base class for encryption algorithms."""
diff --git a/src/cryptojwt/jwx.py b/src/cryptojwt/jwx.py
index 73a98d9c..b941a497 100644
--- a/src/cryptojwt/jwx.py
+++ b/src/cryptojwt/jwx.py
@@ -1,6 +1,7 @@
 """A basic class on which to build the JWS and JWE classes."""
 import json
 import logging
+import warnings
 
 import requests
 
@@ -8,6 +9,7 @@
 from cryptojwt.key_bundle import KeyBundle
 
 from .exception import HeaderError
+from .jwe import DEPRECATED
 from .jwk.jwk import key_from_jwk_dict
 from .jwk.rsa import RSAKey
 from .jwk.rsa import import_rsa_key
@@ -91,6 +93,8 @@ def __init__(self, msg=None, with_digest=False, httpc=None, **kwargs):
                         raise ValueError("x5u")
                 else:
                     self._dict[key] = _val
+                if key in DEPRECATED and _val in DEPRECATED[key]:
+                    warnings.warn(f"{key}={_val} deprecated")
 
     def _set_jwk(self, val):
         if isinstance(val, dict):