diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 0c992bf..519b5b4 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -7016,7 +7016,7 @@
 #endif /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
         switch (ret) {
             case 0: /*ok*/
-            case MBEDTLS_ERR_OID_NOT_FOUND:
+            case MBEDTLS_ERR_X509_UNKNOWN_OID:
                 /* Ignore certificate with an unknown algorithm: maybe a
                    prior certificate was already trusted. */
                 break;
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 70175e0..44525dd 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -505,7 +505,7 @@
         switch (ret) {
             case 0: /*ok*/
                 break;
-            case MBEDTLS_ERR_OID_NOT_FOUND:
+            case MBEDTLS_ERR_X509_UNKNOWN_OID:
                 /* Ignore certificate with an unknown algorithm: maybe a
                    prior certificate was already trusted. */
                 break;
diff --git a/library/x509.c b/library/x509.c
index fe4e3e3..54275eb 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -314,7 +314,7 @@
         /* Only MFG1 is recognised for now */
         if (MBEDTLS_OID_CMP(MBEDTLS_OID_MGF1, &alg_id) != 0) {
             return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE,
-                                     MBEDTLS_ERR_OID_NOT_FOUND);
+                                     MBEDTLS_ERR_X509_UNKNOWN_OID);
         }
 
         /* Parse HashAlgorithm */
diff --git a/library/x509_oid.c b/library/x509_oid.c
index 0a5da54..3517ee3 100644
--- a/library/x509_oid.c
+++ b/library/x509_oid.c
@@ -66,7 +66,7 @@
     int FN_NAME(const mbedtls_asn1_buf *oid, ATTR1_TYPE * ATTR1)                  \
     {                                                                       \
         const TYPE_T *data = oid_ ## TYPE_NAME ## _from_asn1(oid);        \
-        if (data == NULL) return MBEDTLS_ERR_OID_NOT_FOUND;            \
+        if (data == NULL) return MBEDTLS_ERR_X509_UNKNOWN_OID;            \
         *ATTR1 = data->descriptor.ATTR1;                                    \
         return 0;                                                        \
     }
@@ -80,7 +80,7 @@
     int FN_NAME(const mbedtls_asn1_buf *oid, ATTR1_TYPE * ATTR1)                  \
     {                                                                       \
         const TYPE_T *data = oid_ ## TYPE_NAME ## _from_asn1(oid);        \
-        if (data == NULL) return MBEDTLS_ERR_OID_NOT_FOUND;            \
+        if (data == NULL) return MBEDTLS_ERR_X509_UNKNOWN_OID;            \
         *ATTR1 = data->ATTR1;                                               \
         return 0;                                                        \
     }
@@ -95,7 +95,7 @@
                 ATTR2_TYPE * ATTR2)              \
     {                                                                           \
         const TYPE_T *data = oid_ ## TYPE_NAME ## _from_asn1(oid);            \
-        if (data == NULL) return MBEDTLS_ERR_OID_NOT_FOUND;                 \
+        if (data == NULL) return MBEDTLS_ERR_X509_UNKNOWN_OID;                 \
         *(ATTR1) = data->ATTR1;                                                 \
         *(ATTR2) = data->ATTR2;                                                 \
         return 0;                                                            \
@@ -117,7 +117,7 @@
             }                                                                   \
             cur++;                                                              \
         }                                                                       \
-        return MBEDTLS_ERR_OID_NOT_FOUND;                                    \
+        return MBEDTLS_ERR_X509_UNKNOWN_OID;                                    \
     }
 
 /*
@@ -138,7 +138,7 @@
             }                                                                   \
             cur++;                                                              \
         }                                                                       \
-        return MBEDTLS_ERR_OID_NOT_FOUND;                                   \
+        return MBEDTLS_ERR_X509_UNKNOWN_OID;                                   \
     }
 
 /*
diff --git a/library/x509_oid.h b/library/x509_oid.h
index 46cfd54..6b2da98 100644
--- a/library/x509_oid.h
+++ b/library/x509_oid.h
@@ -19,9 +19,6 @@
 
 #include "mbedtls/md.h"
 
-/** OID is not found. */
-#define MBEDTLS_ERR_OID_NOT_FOUND                         -0x002E
-
 /*
  * Maximum number of OID components allowed
  */
@@ -459,7 +456,7 @@
  * \param oid      OID to use
  * \param ext_type place to store the extension type
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_x509_ext_type(const mbedtls_asn1_buf *oid, int *ext_type);
 
@@ -470,7 +467,7 @@
  * \param oid      OID to use
  * \param short_name    place to store the string pointer
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_attr_short_name(const mbedtls_asn1_buf *oid, const char **short_name);
 
@@ -481,7 +478,7 @@
  * \param md_alg   place to store message digest algorithm
  * \param pk_alg   place to store public key algorithm
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_sig_alg(const mbedtls_asn1_buf *oid,
                                  mbedtls_md_type_t *md_alg, mbedtls_pk_type_t *pk_alg);
@@ -492,7 +489,7 @@
  * \param oid      OID to use
  * \param desc     place to store string pointer
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_sig_alg_desc(const mbedtls_asn1_buf *oid, const char **desc);
 
@@ -504,7 +501,7 @@
  * \param oid      place to store ASN.1 OID string pointer
  * \param olen     length of the OID
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_oid_by_sig_alg(mbedtls_pk_type_t pk_alg, mbedtls_md_type_t md_alg,
                                         const char **oid, size_t *olen);
@@ -515,7 +512,7 @@
  * \param oid      OID to use
  * \param md_alg   place to store message digest algorithm
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_md_alg(const mbedtls_asn1_buf *oid, mbedtls_md_type_t *md_alg);
 
@@ -526,7 +523,7 @@
  * \param oid      OID to use
  * \param desc     place to store string pointer
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_extended_key_usage(const mbedtls_asn1_buf *oid, const char **desc);
 #endif
@@ -537,7 +534,7 @@
  * \param oid      OID to use
  * \param desc     place to store string pointer
  *
- * \return         0 if successful, or MBEDTLS_ERR_OID_NOT_FOUND
+ * \return         0 if successful, or MBEDTLS_ERR_X509_UNKNOWN_OID
  */
 int mbedtls_x509_oid_get_certificate_policies(const mbedtls_asn1_buf *oid, const char **desc);