diff --git a/sys/include/net/l2filter.h b/sys/include/net/l2filter.h
index e421861148..11f999a900 100644
--- a/sys/include/net/l2filter.h
+++ b/sys/include/net/l2filter.h
@@ -83,8 +83,10 @@ typedef struct {
  * @pre     @p addr != NULL
  * @pre     @p addr_maxlen <= @ref CONFIG_L2FILTER_ADDR_MAXLEN
  *
- * @return  0 on success
- * @return  -ENOMEM if no empty slot left in list
+ * @retval  0 on success
+ * @retval  -ENOMEM if no empty slot left in list
+ * @retval  -EINVAL if `addr_len > CONFIG_L2FILTER_ADDR_MAXLEN` **AND** `NDEBUG` is enabled.
+ *          Otherwise this condition will trip an `assert()`.
  */
 int l2filter_add(l2filter_t *list, const void *addr, size_t addr_len);
 
diff --git a/sys/net/link_layer/l2filter/l2filter.c b/sys/net/link_layer/l2filter/l2filter.c
index 02b32584ae..be01435015 100644
--- a/sys/net/link_layer/l2filter/l2filter.c
+++ b/sys/net/link_layer/l2filter/l2filter.c
@@ -44,7 +44,11 @@ void l2filter_init(l2filter_t *list)
 
 int l2filter_add(l2filter_t *list, const void *addr, size_t addr_len)
 {
-    assert(list && addr && (addr_len <= CONFIG_L2FILTER_ADDR_MAXLEN));
+    assert(list && addr);
+    if (addr_len > CONFIG_L2FILTER_ADDR_MAXLEN) {
+        assert(0);
+        return -EINVAL;
+    }
 
     int res = -ENOMEM;