diff --git a/LibC/unistd.cpp b/LibC/unistd.cpp
index 1ad4db0d6e..9082d5d92a 100644
--- a/LibC/unistd.cpp
+++ b/LibC/unistd.cpp
@@ -416,4 +416,9 @@ int create_thread(int(*entry)(void*), void* argument)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int ftruncate(int fd, off_t length)
+{
+    ASSERT_NOT_REACHED();
+}
+
 }
diff --git a/LibC/unistd.h b/LibC/unistd.h
index 27f0c73a88..5f38e15b63 100644
--- a/LibC/unistd.h
+++ b/LibC/unistd.h
@@ -80,6 +80,7 @@ long fpathconf(int fd, int name);
 long pathconf(const char *path, int name);
 char* getlogin();
 int chown(const char* pathname, uid_t, gid_t);
+int ftruncate(int fd, off_t length);
 
 enum {
     _PC_NAME_MAX,