diff --git a/library/x509.c b/library/x509.c
index 446bf24..f574055 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -865,7 +865,10 @@
                 p += ret;
                 ret = mbedtls_snprintf(p, n, "=");
                 print_hexstring = 1;
-            } else {
+            } else if (ret == MBEDTLS_ERR_OID_BUF_TOO_SMALL) {
+                return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+            }
+            else {
                 ret = mbedtls_snprintf(p, n, "\?\?=");
             }
         }