diff --git a/crypto/evp_extra/evp_asn1.c b/crypto/evp_extra/evp_asn1.c
index 9765d3916d..e394494cb0 100644
--- a/crypto/evp_extra/evp_asn1.c
+++ b/crypto/evp_extra/evp_asn1.c
@@ -75,7 +75,8 @@ static const EVP_PKEY_ASN1_METHOD *parse_key_type(CBS *cbs) {
     return NULL;
   }
 
-  const EVP_PKEY_ASN1_METHOD *const *asn1_methods = AWSLC_non_fips_pkey_evp_asn1_methods();
+  const EVP_PKEY_ASN1_METHOD *const *asn1_methods =
+      AWSLC_non_fips_pkey_evp_asn1_methods();
   for (size_t i = 0; i < ASN1_EVP_PKEY_METHODS; i++) {
     const EVP_PKEY_ASN1_METHOD *method = asn1_methods[i];
     if (CBS_len(&oid) == method->oid_len &&
@@ -84,6 +85,12 @@ static const EVP_PKEY_ASN1_METHOD *parse_key_type(CBS *cbs) {
     }
   }
 
+  // Special logic to handle the rarer |NID_rsa|.
+  // https://www.itu.int/ITU-T/formal-language/itu-t/x/x509/2008/AlgorithmObjectIdentifiers.html
+  if (OBJ_cbs2nid(&oid) == NID_rsa) {
+    return &rsa_asn1_meth;
+  }
+
   return NULL;
 }
 
diff --git a/crypto/evp_extra/evp_tests.txt b/crypto/evp_extra/evp_tests.txt
index d0c06038a1..31026be280 100644
--- a/crypto/evp_extra/evp_tests.txt
+++ b/crypto/evp_extra/evp_tests.txt
@@ -33,10 +33,13 @@ PublicKey = RSA-2048-Even-Modulus
 Input = 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
 Error = BAD_RSA_PARAMETERS
 
-# The same key but with missing parameters rather than a NULL.
-PublicKey = RSA-2048-SPKI-Invalid
+# The same key but with missing parameters rather than a NULL. This parses correctly in OpenSSL, so we let this parse
+# to gain compatibility.
+PublicKey = RSA-2048-SPKI-MISSING-NULL
+Type = RSA
 Input = 30820120300b06092a864886f70d0101010382010f003082010a0282010100cd0081ea7b2ae1ea06d59f7c73d9ffb94a09615c2e4ba7c636cef08dd3533ec3185525b015c769b99a77d6725bf9c3532a9b6e5f6627d5fb85160768d3dda9cbd35974511717dc3d309d2fc47ee41f97e32adb7f9dd864a1c4767a666ecd71bc1aacf5e7517f4b38594fea9b05e42d5ada9912008013e45316a4d9bb8ed086b88d28758bacaf922d46a868b485d239c9baeb0e2b64592710f42b2d1ea0a4b4802c0becab328f8a68b0073bdb546feea9809d2849912b390c1532bc7e29c7658f8175fae46f34332ff87bcab3e40649b98577869da0ea718353f0722754886913648760d122be676e0fc483dd20ffc31bda96a31966c9aa2e75ad03de47e1c44f0203010001
-Error = DECODE_ERROR
+# The key re-encodes with the missing NULL parameter in place.
+Output = 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
 
 # The same key but with an incorrectly-encoded length prefix.
 PublicKey = RSA-2048-SPKI-Invalid2
diff --git a/crypto/evp_extra/p_rsa_asn1.c b/crypto/evp_extra/p_rsa_asn1.c
index 04235950cc..05f5881112 100644
--- a/crypto/evp_extra/p_rsa_asn1.c
+++ b/crypto/evp_extra/p_rsa_asn1.c
@@ -86,16 +86,13 @@ static int rsa_pub_encode(CBB *out, const EVP_PKEY *key) {
 }
 
 static int rsa_pub_decode(EVP_PKEY *out, CBS *params, CBS *key) {
-  // See RFC 3279, section 2.3.1.
-
-  // The parameters must be NULL.
-  CBS null;
-  if (!CBS_get_asn1(params, &null, CBS_ASN1_NULL) ||
-      CBS_len(&null) != 0 ||
-      CBS_len(params) != 0) {
-    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
-    return 0;
-  }
+  // The IETF specification defines that the parameters must be
+  // NULL. See RFC 3279, section 2.3.1.
+  // There is also an ITU-T X.509 specification that is rarely seen,
+  // which defines a KeySize parameter. See ITU-T X.509 2008-11
+  // AlgorithmObjectIdentifiers.
+  //
+  // OpenSSL ignores both parameters when parsing, however.
 
   RSA *rsa = RSA_parse_public_key(key);
   if (rsa == NULL || CBS_len(key) != 0) {
diff --git a/crypto/obj/obj_xref.c b/crypto/obj/obj_xref.c
index e6646e8d7b..3b59258593 100644
--- a/crypto/obj/obj_xref.c
+++ b/crypto/obj/obj_xref.c
@@ -74,6 +74,10 @@ static const nid_triple kTriples[] = {
     {NID_sha256WithRSAEncryption, NID_sha256, NID_rsaEncryption},
     {NID_sha384WithRSAEncryption, NID_sha384, NID_rsaEncryption},
     {NID_sha512WithRSAEncryption, NID_sha512, NID_rsaEncryption},
+    // RSA ITU-T X.509. These are rare and we map them to the more
+    // common |NID_rsaEncryption| instead for simplicity.
+    {NID_md5WithRSA, NID_md5, NID_rsaEncryption},
+    {NID_sha1WithRSA, NID_sha1, NID_rsaEncryption},
     // DSA.
     {NID_dsaWithSHA1, NID_sha1, NID_dsa},
     {NID_dsaWithSHA1_2, NID_sha1, NID_dsa_2},
diff --git a/crypto/x509/x509_test.cc b/crypto/x509/x509_test.cc
index e811828fd5..cee8e27203 100644
--- a/crypto/x509/x509_test.cc
+++ b/crypto/x509/x509_test.cc
@@ -5876,6 +5876,35 @@ TEST(X509Test, NamePrint) {
   }
 }
 
+
+// kLargeSerialPEM is a certificate with a large serial number.
+static const char kRareRSAPEM[] = R"(
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+)";
+
+TEST(X509Test, ITUT_X509_nid_rsa) {
+  bssl::UniquePtr<X509> cert(CertFromPEM(kRareRSAPEM));
+  ASSERT_TRUE(cert);
+
+  EXPECT_TRUE(X509_get_X509_PUBKEY(cert.get()));
+  bssl::UniquePtr<EVP_PKEY> evp_pkey(X509_get_pubkey(cert.get()));
+  EXPECT_TRUE(evp_pkey);
+}
+
 // kLargeSerialPEM is a certificate with a large serial number.
 static const char kLargeSerialPEM[] = R"(
 -----BEGIN CERTIFICATE-----