diff --git a/cpu/atmega32u4/include/cpu_conf.h b/cpu/atmega32u4/include/cpu_conf.h
index 31812c92b1..65c6ea2c3e 100644
--- a/cpu/atmega32u4/include/cpu_conf.h
+++ b/cpu/atmega32u4/include/cpu_conf.h
@@ -39,7 +39,9 @@ extern "C" {
 #define THREAD_STACKSIZE_DEFAULT   (256)
 #endif
 
+#ifndef THREAD_STACKSIZE_IDLE
 #define THREAD_STACKSIZE_IDLE      (128)
+#endif
 /** @} */
 
 #ifdef __cplusplus