diff --git a/m-core.h b/m-core.h
index 0c11c97e..c61bb18b 100644
--- a/m-core.h
+++ b/m-core.h
@@ -1373,6 +1373,14 @@
 
 /* C11 MACROS */
 
+/* Maximum number of characters of an internal identifier
+   including final null char. Bigger than 
+   63 significant initial characters of C11 standard (§5.2.4.1)
+   Can be overloaded by user if needed.  */
+#ifndef M_MAX_IDENTIFIER_LENGTH
+#define M_MAX_IDENTIFIER_LENGTH 128 /* (including of final null char) */
+#endif
+
 /* Return the string format of a variable */
 #define M_PRINTF_FORMAT(x)                                              \
   _Generic(((void)0,(x)),                                               \
diff --git a/m-serial-json.h b/m-serial-json.h
index 2956b0c6..2803c96b 100644
--- a/m-serial-json.h
+++ b/m-serial-json.h
@@ -199,8 +199,31 @@ m_serial_json_read_tuple_id(m_serial_read_t serial, const char *const field_name
   FILE *f = (FILE*) serial->data[0];
   int c = m_serial_json_read_skip(f);
   if (c == '}') return M_SERIAL_OK_DONE;
+  if (c == ',') {
+     // If first call of read_tuple_id, it is a failure
+     if (*id == -1) return M_SERIAL_FAIL;
+     c = m_serial_json_read_skip(f);
+  }
   if (c != '"') return M_SERIAL_FAIL;
-  
+  /* Read the field in the JSON */
+  char field[M_MAX_IDENTIFIER_LENGTH];
+  int n = 0;
+  do {
+     c =fgetc(f);
+     field[n++] = c;
+  } while (n < M_MAX_IDENTIFIER_LENGTH && c != EOF && c != '\"');
+  field[--n] = 0;
+  if (c != '"') return M_SERIAL_FAIL;
+  c =fgetc(f);
+  if (c != ':') return M_SERIAL_FAIL;
+  /* Search for field in field_name */
+  for(n = 0; n < max; n++) {
+     if (strcmp(field, field_name[n]) == 0)
+         break;
+  }
+  if (n == max) return M_SERIAL_FAIL;
+  *id = n;
+  return M_SERIAL_OK_CONTINUE;
 }
 
 static inline  m_serial_return_code_t m_serial_json_read_variant_start(m_serial_read_t serial, const char *const field_name[], const int max, int*id){ return M_SERIAL_FAIL; }
diff --git a/m-tuple.h b/m-tuple.h
index 787324cc..6a559617 100644
--- a/m-tuple.h
+++ b/m-tuple.h
@@ -435,19 +435,20 @@ namespace m_tuple {
   static inline m_serial_return_code_t                                  \
   M_C(name, _in_serial)(M_C(name,_t) el, m_serial_read_t f) {           \
     assert (f != NULL && el != NULL);                                   \
-    int index = 0;                                                      \
+    int index = -1;                                                     \
     const int field_max = M_NARGS(__VA_ARGS__);                         \
     static const char *const field_name[] =                             \
-      { M_MAP(TUPLE_STRINGIFY_NAME, __VA_ARGS__) };                     \
+      { M_REDUCE(TUPLE_STRINGIFY_NAME, M_ID, __VA_ARGS__) };            \
     m_serial_return_code_t ret;                                         \
     ret = f->interface->read_tuple_start(f);                            \
-    while (ret != M_SERIAL_OK_CONTINUE) {                               \
+    while (ret == M_SERIAL_OK_CONTINUE) {                               \
       ret = f->interface->read_tuple_id(f, field_name, field_max, &index); \
       if (ret == M_SERIAL_OK_CONTINUE) {                                \
         switch (1+index) {                                              \
           M_MAP2(TUPLE_DEFINE_IN_SERIAL_FUNC , name, __VA_ARGS__)       \
         default: assert(0);                                             \
         }                                                               \
+        ret = (ret == M_SERIAL_OK_DONE) ? M_SERIAL_OK_CONTINUE : M_SERIAL_FAIL; \
       }                                                                 \
     }                                                                   \
     return ret;                                                         \