diff --git a/library/x509_create.c b/library/x509_create.c
index 46ffc9c..9d40db0 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -146,6 +146,11 @@
         return NULL;
     }
     oid = mbedtls_calloc(1, oid_buf->len + 1);
+    if(oid == NULL) {
+        mbedtls_free(oid_buf->p);
+        mbedtls_free(oid_buf);
+        return MBEDTLS_ERR_X509_ALLOC_FAILED;
+    }
     memcpy(oid, oid_buf->p, oid_buf->len);
     oid[oid_buf->len + 1] = '\0';
     mbedtls_free(oid_buf->p);