diff --git a/sys/posix/pthread/pthread.c b/sys/posix/pthread/pthread.c
index 71a55a94c0..b11ae62900 100644
--- a/sys/posix/pthread/pthread.c
+++ b/sys/posix/pthread/pthread.c
@@ -35,11 +35,11 @@
 #define ENABLE_DEBUG (1)
 
 #if ENABLE_DEBUG
-#define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_MAIN
-#define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_MAIN
+#   define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_MAIN
+#   define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_MAIN
 #else
-#define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_DEFAULT
-#define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_DEFAULT
+#   define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_DEFAULT
+#   define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_DEFAULT
 #endif
 
 #include "debug.h"
@@ -68,7 +68,7 @@ static struct mutex_t pthread_mutex;
 
 static volatile int pthread_reaper_pid = -1;
 
-char pthread_reaper_stack[PTHREAD_REAPER_STACKSIZE];
+static char pthread_reaper_stack[PTHREAD_REAPER_STACKSIZE];
 
 static void pthread_start_routine(void)
 {