diff --git a/cpu/native/syscalls.c b/cpu/native/syscalls.c
index 8c2b84cd00..d4fdefdb9a 100644
--- a/cpu/native/syscalls.c
+++ b/cpu/native/syscalls.c
@@ -145,7 +145,7 @@ void free(void *ptr)
     _native_syscall_leave();
 }
 
-int _native_in_calloc;
+int _native_in_calloc = 0;
 void *calloc(size_t nmemb, size_t size)
 {
     /* dynamically load calloc when it's needed - this is necessary to