diff --git a/library/x509_crt.c b/library/x509_crt.c
index 0aa4f4c..8086cc0 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -397,17 +397,17 @@
             return( 0 );
         }
 
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT, ret ) );
     }
 
     end = *p + len;
 
     if( ( ret = mbedtls_asn1_get_int( p, end, ver ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_VERSION + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_VERSION, ret ) );
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_VERSION +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_VERSION,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     return( 0 );
 }
@@ -427,7 +427,7 @@
 
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_DATE + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_DATE, ret ) );
 
     end = *p + len;
 
@@ -438,8 +438,8 @@
         return( ret );
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_DATE +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_DATE,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     return( 0 );
 }
@@ -464,7 +464,7 @@
         if( ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
             return( 0 );
 
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT, ret ) );
     }
 
     uid->p = *p;
@@ -491,7 +491,7 @@
 
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( *p == end )
         return( 0 );
@@ -502,7 +502,7 @@
             ret = mbedtls_asn1_get_int( p, end, ca_istrue );
 
         if( ret != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         if( *ca_istrue != 0 )
             *ca_istrue = 1;
@@ -512,17 +512,17 @@
         return( 0 );
 
     if( ( ret = mbedtls_asn1_get_int( p, end, max_pathlen ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     /* Do not accept max_pathlen equal to INT_MAX to avoid a signed integer
      * overflow, which is an undefined behavior. */
     if( *max_pathlen == INT_MAX )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_INVALID_LENGTH ) );
 
     (*max_pathlen)++;
 
@@ -537,11 +537,11 @@
     mbedtls_x509_bitstring bs = { 0, 0, NULL };
 
     if( ( ret = mbedtls_asn1_get_bitstring( p, end, &bs ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( bs.len != 1 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_INVALID_LENGTH ) );
 
     /* Get actual bitstring */
     *ns_cert_type = *bs.p;
@@ -557,11 +557,11 @@
     mbedtls_x509_bitstring bs = { 0, 0, NULL };
 
     if( ( ret = mbedtls_asn1_get_bitstring( p, end, &bs ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( bs.len < 1 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_INVALID_LENGTH ) );
 
     /* Get actual bitstring */
     *key_usage = 0;
@@ -585,12 +585,12 @@
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
     if( ( ret = mbedtls_asn1_get_sequence_of( p, end, ext_key_usage, MBEDTLS_ASN1_OID ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     /* Sequence length must be >= 1 */
     if( ext_key_usage->buf.p == NULL )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_INVALID_LENGTH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_INVALID_LENGTH ) );
 
     return( 0 );
 }
@@ -635,11 +635,11 @@
     /* Get main sequence tag */
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( *p + len != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     while( *p < end )
     {
@@ -649,13 +649,13 @@
         tag = **p;
         (*p)++;
         if( ( ret = mbedtls_asn1_get_len( p, end, &tag_len ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         if( ( tag & MBEDTLS_ASN1_TAG_CLASS_MASK ) !=
                 MBEDTLS_ASN1_CONTEXT_SPECIFIC )
         {
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                    MBEDTLS_ERR_ASN1_UNEXPECTED_TAG ) );
         }
 
         /*
@@ -691,8 +691,8 @@
             cur->next = mbedtls_calloc( 1, sizeof( mbedtls_asn1_sequence ) );
 
             if( cur->next == NULL )
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                        MBEDTLS_ERR_ASN1_ALLOC_FAILED );
+                return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                        MBEDTLS_ERR_ASN1_ALLOC_FAILED ) );
 
             cur = cur->next;
         }
@@ -708,8 +708,8 @@
     cur->next = NULL;
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     return( 0 );
 }
@@ -776,18 +776,18 @@
     ret = mbedtls_asn1_get_tag( p, end, &len,
                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE );
     if( ret != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( *p + len != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     /*
      * Cannot be an empty sequence.
      */
     if( len == 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     while( *p < end )
     {
@@ -799,13 +799,13 @@
          */
         if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
                 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         policy_end = *p + len;
 
         if( ( ret = mbedtls_asn1_get_tag( p, policy_end, &len,
                                           MBEDTLS_ASN1_OID ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         policy_oid.tag = MBEDTLS_ASN1_OID;
         policy_oid.len = len;
@@ -833,8 +833,8 @@
             cur->next = mbedtls_calloc( 1, sizeof( mbedtls_asn1_sequence ) );
 
             if( cur->next == NULL )
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                        MBEDTLS_ERR_ASN1_ALLOC_FAILED );
+                return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                        MBEDTLS_ERR_ASN1_ALLOC_FAILED ) );
 
             cur = cur->next;
         }
@@ -854,7 +854,7 @@
         {
             if( ( ret = mbedtls_asn1_get_tag( p, policy_end, &len,
                      MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+                return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
             /*
              * Skip the optional policy qualifiers.
              */
@@ -862,16 +862,16 @@
         }
 
         if( *p != policy_end )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
 
     /* Set final sequence entry's next pointer to NULL */
     cur->next = NULL;
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     return( parse_ret );
 }
@@ -911,14 +911,14 @@
 
         if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
                 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         end_ext_data = *p + len;
 
         /* Get extension ID */
         if( ( ret = mbedtls_asn1_get_tag( p, end_ext_data, &extn_oid.len,
                                           MBEDTLS_ASN1_OID ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         extn_oid.tag = MBEDTLS_ASN1_OID;
         extn_oid.p = *p;
@@ -927,19 +927,19 @@
         /* Get optional critical */
         if( ( ret = mbedtls_asn1_get_bool( p, end_ext_data, &is_critical ) ) != 0 &&
             ( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG ) )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         /* Data should be octet string type */
         if( ( ret = mbedtls_asn1_get_tag( p, end_ext_data, &len,
                 MBEDTLS_ASN1_OCTET_STRING ) ) != 0 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
         start_ext_octet = *p;
         end_ext_octet = *p + len;
 
         if( end_ext_octet != end_ext_data )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
         /*
          * Detect supported extensions
@@ -965,8 +965,8 @@
             if( is_critical )
             {
                 /* Data is marked as critical: fail */
-                return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                        MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+                return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                        MBEDTLS_ERR_ASN1_UNEXPECTED_TAG ) );
             }
 #endif
             continue;
@@ -1059,8 +1059,8 @@
     }
 
     if( *p != end )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
 
     return( 0 );
 }
@@ -1138,7 +1138,7 @@
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
     {
         mbedtls_x509_crt_free( crt );
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT, ret ) );
     }
 
     end = p + len;
@@ -1185,7 +1185,7 @@
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
     {
         mbedtls_x509_crt_free( crt );
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT, ret ) );
     }
 
     if( ( ret = mbedtls_x509_get_name( &p, p + len, &crt->issuer ) ) != 0 )
@@ -1218,7 +1218,7 @@
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
     {
         mbedtls_x509_crt_free( crt );
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT, ret ) );
     }
 
     if( len && ( ret = mbedtls_x509_get_name( &p, p + len, &crt->subject ) ) != 0 )
@@ -1283,8 +1283,8 @@
     if( p != end )
     {
         mbedtls_x509_crt_free( crt );
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
 
     end = crt_end;
@@ -1322,8 +1322,8 @@
     if( p != end )
     {
         mbedtls_x509_crt_free( crt );
-        return( MBEDTLS_ERR_X509_INVALID_FORMAT +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_FORMAT,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
 
     return( 0 );
@@ -1706,7 +1706,7 @@
 
     if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
                                       MBEDTLS_ASN1_OID ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     cur_oid.tag = MBEDTLS_ASN1_OID;
     cur_oid.p = p;
@@ -1723,20 +1723,20 @@
     if( p + len >= end )
     {
         mbedtls_platform_zeroize( other_name, sizeof( *other_name ) );
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
     p += len;
     if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
                      MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
-       return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+       return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     if( ( ret = mbedtls_asn1_get_tag( &p, end, &len, MBEDTLS_ASN1_OID ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     other_name->value.hardware_module_name.oid.tag = MBEDTLS_ASN1_OID;
     other_name->value.hardware_module_name.oid.p = p;
@@ -1745,13 +1745,13 @@
     if( p + len >= end )
     {
         mbedtls_platform_zeroize( other_name, sizeof( *other_name ) );
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
     p += len;
     if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
                                       MBEDTLS_ASN1_OCTET_STRING ) ) != 0 )
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret ) );
 
     other_name->value.hardware_module_name.val.tag = MBEDTLS_ASN1_OCTET_STRING;
     other_name->value.hardware_module_name.val.p = p;
@@ -1761,8 +1761,8 @@
     {
         mbedtls_platform_zeroize( other_name,
                                   sizeof( *other_name ) );
-        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+        return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH ) );
     }
     return( 0 );
 }