diff --git a/tests/pkg_ucglib/Makefile b/tests/pkg_ucglib/Makefile
index a37fd25e15..d129aa2648 100644
--- a/tests/pkg_ucglib/Makefile
+++ b/tests/pkg_ucglib/Makefile
@@ -20,6 +20,7 @@ endif
 
 # features depend on output type
 ifeq ($(TEST_OUTPUT),2)
+  CFLAGS += -DTHREAD_STACKSIZE_MAIN=48*1024
   USEMODULE += ucglib_sdl
 endif
 
diff --git a/tests/pkg_ucglib/main.c b/tests/pkg_ucglib/main.c
index 0eef82921a..580291611a 100644
--- a/tests/pkg_ucglib/main.c
+++ b/tests/pkg_ucglib/main.c
@@ -62,6 +62,10 @@
 
 #include "logo.h"
 
+#if TEST_OUTPUT == TEST_OUTPUT_SDL
+int ucg_sdl_get_key(void);
+#endif
+
 int main(void)
 {
     uint32_t screen = 0;