diff --git a/sys/malloc_thread_safe/malloc_wrappers.c b/sys/malloc_thread_safe/malloc_wrappers.c
index be81c82066..138dae65a2 100644
--- a/sys/malloc_thread_safe/malloc_wrappers.c
+++ b/sys/malloc_thread_safe/malloc_wrappers.c
@@ -14,41 +14,49 @@
  * @author  Gunar Schorcht <gunar@schorcht.net>
  */
 
+#include "assert.h"
 #include "irq.h"
+#include "mutex.h"
 
 extern void *__real_malloc(size_t size);
 extern void __real_free(void *ptr);
 extern void *__real_calloc(size_t nmemb, size_t size);
 extern void *__real_realloc(void *ptr, size_t size);
 
+static mutex_t _lock;
+
 void *__wrap_malloc(size_t size)
 {
-    unsigned state = irq_disable();
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
     void *ptr = __real_malloc(size);
-    irq_restore(state);
+    mutex_unlock(&_lock);
     return ptr;
 }
 
 void __wrap_free(void *ptr)
 {
-    unsigned state = irq_disable();
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
     __real_free(ptr);
-    irq_restore(state);
+    mutex_unlock(&_lock);
 }
 
 void *__wrap_calloc(size_t nmemb, size_t size)
 {
-    unsigned state = irq_disable();
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
     void *ptr = __real_calloc(nmemb, size);
-    irq_restore(state);
+    mutex_unlock(&_lock);
     return ptr;
 }
 
 void *__wrap_realloc(void *ptr, size_t size)
 {
-    unsigned state = irq_disable();
+    assert(!irq_is_in());
+    mutex_lock(&_lock);
     void *new = __real_realloc(ptr, size);
-    irq_restore(state);
+    mutex_unlock(&_lock);
     return new;
 }