diff --git a/README.md b/README.md
index 0e477b68..8c726695 100644
--- a/README.md
+++ b/README.md
@@ -1929,6 +1929,7 @@ and `it1` references the inserted element in `list1`.
 Move all the element of the list `list2` into the list `list1`,
 moving the last element of `list2` after the first element of `list1`.
 Afterwards, `list2` remains initialized but is emptied.
+`list1` and `list2` shall reference different objects.
 
 ##### `void name_reverse(name_t list)`
 
@@ -2082,6 +2083,7 @@ Afterwards, `it` points to the next element of `list2`.
 Move all the element of the list `list2` into the list `list1`,
 moving the last element of `list2` after the first element of `list1`.
 Afterwards, `list2` is emptied.
+`list1` and `list2` shall reference different objects.
 
 ##### `void name_reverse(name_t list)`
 
@@ -2294,6 +2296,7 @@ comparisons.
 
 Move all the elements of the array `array2` to the end of the array `array1`.
 Afterwards, `array2` is empty.
+`array1` and `array2` shall reference different objects.
 
 _________________
 
@@ -2702,6 +2705,7 @@ If there is the same key between `dict2` into `dict1`,
 then their values are added (as per the `ADD` method of the value type).
 Afterward `dict2` is reset (i.e. empty).
 This method is only defined if the value type defines an `ADD` method.
+`dict1` and `dict2` shall reference different objects.
 
 _________________
 
@@ -4724,6 +4728,7 @@ This method is created only if the `DIV` operator is defined.
 
 Append in `*a` all elements of `*b` and reset `*b`.
 This method is created only if the `SPLICE` operator is defined.
+`a` and `b` shall reference different objects.
 
 ##### `bool name_get(value_type *val, const name_t *a, key_type const key)`
 
@@ -5468,6 +5473,7 @@ Afterwards, `it` points to the next element of `list2`.
 Move all the element of `list2` into `list1`, moving the last element
 of `list2` after the first element of `list1`.
 Afterwards, `list2` is emptied.
+`list1` and `list2` shall reference different objects.
 
 _________________
 
@@ -6602,6 +6608,7 @@ Append the buffer of 'n' bytes to the byte string `v`
 
 Append the byte string `src` to the byte string `dst`,
 emptying 'src' afterwards. 
+`dst` and `src` shall reference different objects.
 
 ##### `uint8_t bstring_pop_back (bstring_t v)`
 
diff --git a/m-array.h b/m-array.h
index 7061986f..7f3a2267 100644
--- a/m-array.h
+++ b/m-array.h
@@ -958,6 +958,7 @@
   {                                                                           \
     M_ARRA4_CONTRACT(a1);                                                     \
     M_ARRA4_CONTRACT(a2);                                                     \
+    M_ASSERT(a1 != a2);                                                       \
     if (M_LIKELY (a2->size > 0)) {                                            \
       size_t newSize = a1->size + a2->size;                                   \
       /* To overflow newSize, we need to a1 and a2 a little bit above         \
diff --git a/m-bstring.h b/m-bstring.h
index 50257bcf..37dbb841 100644
--- a/m-bstring.h
+++ b/m-bstring.h
@@ -214,7 +214,9 @@ m_bstring_push_back_bytes (m_bstring_t v, size_t n, const void *buffer)
 M_INLINE void
 m_bstring_splice(m_bstring_t dst, m_bstring_t src)
 {
+    M_BSTRING_CONTRACT (dst);
     M_BSTRING_CONTRACT (src);
+    M_ASSERT(src != dst);
     m_bstring_push_back_bytes(dst, m_bstring_size(src), m_bstr1ng_cstr(src));
     m_bstring_reset(src);
 }
diff --git a/m-dict.h b/m-dict.h
index 5e3d7856..bedbf1ee 100644
--- a/m-dict.h
+++ b/m-dict.h
@@ -1223,6 +1223,7 @@ ARRAY_DEF(m_array_index, m_indexhash_t, M_POD_OPLIST)
   M_F(name, _splice)(dict_t d1, dict_t d2)                                    \
   {                                                                           \
     dict_it_t it;                                                             \
+    M_ASSERT(d1 != d2);                                                       \
     /* NOTE: Despite using set_at, the accessing of the item in d1            \
        is not as random as other uses of the HASH table as d2                 \
        uses the same order than d1 */                                         \