diff --git a/library/ssl_client.h b/library/ssl_client.h
index 8e0c216..be4d067 100644
--- a/library/ssl_client.h
+++ b/library/ssl_client.h
@@ -28,6 +28,7 @@
 
 #include <stddef.h>
 
+MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_write_client_hello( mbedtls_ssl_context *ssl );
 
 #endif /* MBEDTLS_SSL_CLIENT_H */