diff --git a/os/test/include/ch_test.h b/os/test/include/ch_test.h
index 2f95a67e1..3723bfe6e 100644
--- a/os/test/include/ch_test.h
+++ b/os/test/include/ch_test.h
@@ -28,6 +28,8 @@
 #ifndef CH_TEST_H
 #define CH_TEST_H
 
+#include <stdarg.h>
+
 #if defined(TEST_USE_CFG_FILE)
 #include "testconf.h"
 #endif
@@ -345,7 +347,6 @@ static inline msg_t test_execute(BaseSequentialStream *stream,
 }
 #endif
 
-
 /**
  * @brief   Prints a decimal unsigned number.
  *