diff --git a/library/x509.c b/library/x509.c
index c55d038..3997ebd 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -785,7 +785,7 @@
             if( c && strchr( ",=+<>#;\"\\", c ) )
             {
                 if( j + 1 >= sizeof( s ) - 1 )
-                    continue;
+                    return( MBEDTLS_ERR_X509_BUFFER_TOO_SMALL );
                 s[j++] = '\\';
             }
             if( c < 32 || c >= 127 )
diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index 0671606..066d6e4 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -423,6 +423,10 @@
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_SHA1_C
 mbedtls_x509_dn_gets_subject_replace:"data_files/server1.crt":"1234567890,1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234":"":MBEDTLS_ERR_X509_BUFFER_TOO_SMALL
 
+X509 Get Modified DN #5 Name exactly 255 bytes, ending with comma requiring escaping
+depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_SHA1_C
+mbedtls_x509_dn_gets_subject_replace:"data_files/server1.crt":"12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234,":"":MBEDTLS_ERR_X509_BUFFER_TOO_SMALL
+
 X509 Time Expired #1
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_HAVE_TIME_DATE:MBEDTLS_SHA1_C
 mbedtls_x509_time_is_past:"data_files/server1.crt":"valid_from":1