diff --git a/scapy/asn1fields.py b/scapy/asn1fields.py
index a080e1edf2a2678fad93375180751db90a3ec286..6b23f9bd0ea82968bce82c7ba0fe6950301f4271 100644
--- a/scapy/asn1fields.py
+++ b/scapy/asn1fields.py
@@ -402,11 +402,14 @@ class ASN1F_CHOICE(ASN1F_field):
     Multiple types are allowed: ASN1_Packet, ASN1F_field and ASN1F_PACKET(),
     e.g. you could define ASN1F_CHOICE("qualifier", None,
                                        X509_UserNotice,
-                                       ASN1F_X509_CPSuri,
+                                       ASN1F_X509_CPSuri)
+                       or ASN1F_CHOICE("qualifier", None,
                                        ASN1F_PACKET("index", dflt, X509_Pkt,
                                                     implicit_tag=0x82),
                                        explicit_tag=0xa1)
     Other ASN1F_field instances than ASN1F_PACKET instances must not be used.
+    ASN1F_PACKET instances must not be mixed with other types.
+    self.instantiated_choices signals whether only such instances are present.
     """
     holds_packets = 1
     ASN1_tag = ASN1_Class_UNIVERSAL.ANY
diff --git a/scapy/layers/x509.py b/scapy/layers/x509.py
index e0e1e17c54f9f8f91c6335c526b3ea4600e0cdcf..4bd14080911ede4facb128b519fbb34d365fd4d4 100644
--- a/scapy/layers/x509.py
+++ b/scapy/layers/x509.py
@@ -94,7 +94,7 @@ class ECParameters(ASN1_Packet):
     ASN1_root = ASN1F_CHOICE("curve", ASN1_OID("ansip384r1"),
                     ASN1F_OID,      # for named curves
                     ASN1F_NULL,     # for implicit curves
-                    ASN1F_PACKET("curve", None, ECSpecifiedDomain))
+                    ECSpecifiedDomain)
 
 class ECDSAPublicKey(ASN1_Packet):
     ASN1_codec = ASN1_Codecs.BER