diff --git a/cpu/esp32/startup.c b/cpu/esp32/startup.c
index 8dc69e1b51..f07f261068 100644
--- a/cpu/esp32/startup.c
+++ b/cpu/esp32/startup.c
@@ -336,6 +336,10 @@ static NORETURN void IRAM system_init (void)
     /* initialize stdio */
     stdio_init();
 
+    /* disable buffering in stdio */
+    setvbuf(_stdout_r(_REENT), NULL, _IONBF, 0);
+    setvbuf(_stderr_r(_REENT), NULL, _IONBF, 0);
+
     /* trigger static peripheral initialization */
     periph_init();