diff --git a/tests/rng/Makefile b/tests/rng/Makefile
index 7da2cd825f..c772140bd6 100644
--- a/tests/rng/Makefile
+++ b/tests/rng/Makefile
@@ -5,6 +5,10 @@ BOARD_BLACKLIST += nucleo-f031k6 nucleo-f042k6 nucleo-l031k6 pic32-clicker
 BOARD_INSUFFICIENT_MEMORY += arduino-duemilanove arduino-leonardo arduino-nano \
                              arduino-uno
 
+# Default stack with printf + the tests buffer uint32_t[32]/uint8_t[256]
+MAIN_THREAD_SIZE = THREAD_STACKSIZE_DEFAULT+THREAD_EXTRA_STACKSIZE_PRINTF+256
+CFLAGS += -DTHREAD_STACKSIZE_MAIN=\($(MAIN_THREAD_SIZE)\)
+
 # override PRNG if desired (see sys/random for alternatives)
 # USEMODULE += prng_minstd