diff --git a/src/box/box.cc b/src/box/box.cc
index 1be2126ec7ad36659553d59caa9ed16c4e2483a9..386a12e54f2906dbfb5b9a98e87c0ab5e2e0573a 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -124,7 +124,7 @@ recover_snap_row(const void *data)
 	struct space *space = space_find(row->space);
 	Index *index = space_index(space, 0);
 	/* Check to see if the tuple has a sufficient number of fields. */
-	if (unlikely(row->tuple_size < space->max_fieldno)) {
+	if (unlikely(row->tuple_size < space->max_fieldno + 1)) {
 		tnt_raise(IllegalParams,
 			  "tuple must have all indexed fields");
 	}
diff --git a/src/box/key_def.cc b/src/box/key_def.cc
index f668fb23dcaecd1299d6180ae280c321333256f0..29c51c59443a58b79e15ec74e976fab385cff3e7 100644
--- a/src/box/key_def.cc
+++ b/src/box/key_def.cc
@@ -63,13 +63,12 @@ key_def_create(struct key_def *def, struct tarantool_cfg_space_index *cfg_index)
 	def->parts = (struct key_part *) malloc(sizeof(struct key_part) *
 						def->part_count);
 
+	uint32_t cmp_order_size = (def->max_fieldno + 1) * sizeof(uint32_t);
 	/* init compare order array */
-	def->max_fieldno++;
-	def->cmp_order = (uint32_t *) malloc(def->max_fieldno * sizeof(uint32_t));
+	def->cmp_order = (uint32_t *) malloc(cmp_order_size);
 
-	for (uint32_t fieldno = 0; fieldno < def->max_fieldno; fieldno++) {
+	for (uint32_t fieldno = 0; fieldno <= def->max_fieldno; fieldno++)
 		def->cmp_order[fieldno] = UINT32_MAX;
-	}
 
 	/* fill fields and compare order */
 	for (uint32_t k = 0; cfg_index->key_field[k] != NULL; ++k) {
diff --git a/src/box/key_def.h b/src/box/key_def.h
index 3ba9954108857e1fccdc95e06bb78854f0ef6de1..8cc234082736c727c7afdc99b55e3fb07703162d 100644
--- a/src/box/key_def.h
+++ b/src/box/key_def.h
@@ -77,8 +77,8 @@ struct key_def {
 	/* The size of the 'parts' array. */
 	uint32_t part_count;
 	/*
-	 * The size of 'cmp_order' array (= max fieldno in 'parts'
-	 * array).
+	 * Max fieldno in 'parts' array. Defines the size of
+	 * cmp_order array (which is max_fieldno + 1).
 	 */
 	uint32_t max_fieldno;
 	bool is_unique;
diff --git a/src/box/space.cc b/src/box/space.cc
index 9ed0524f044b1263fce2a482cbb3e482f2345bb7..0df76ddf981a923cf26f4f84d1c005dabaece365 100644
--- a/src/box/space.cc
+++ b/src/box/space.cc
@@ -206,7 +206,7 @@ void
 space_validate_tuple(struct space *sp, struct tuple *new_tuple)
 {
 	/* Check to see if the tuple has a sufficient number of fields. */
-	if (new_tuple->field_count < sp->max_fieldno)
+	if (new_tuple->field_count < sp->max_fieldno + 1)
 		tnt_raise(IllegalParams,
 			  "tuple must have all indexed fields");
 
@@ -221,8 +221,6 @@ space_validate_tuple(struct space *sp, struct tuple *new_tuple)
 	uint32_t len;
 	uint32_t fieldno = 0;
 	while ((field = tuple_next(&it, &len))) {
-		if (fieldno == sp->max_fieldno)
-			break;
 		/*
 		 * Check fixed size fields (NUM and NUM64) and
 		 * skip undefined size fields (STRING and UNKNOWN).
@@ -236,6 +234,8 @@ space_validate_tuple(struct space *sp, struct tuple *new_tuple)
 				tnt_raise(ClientError, ER_KEY_FIELD_TYPE,
 					  "NUM64");
 		}
+		if (fieldno == sp->max_fieldno)
+			break;
 		fieldno++;
 	}
 }
@@ -276,14 +276,14 @@ space_init_field_types(struct space *space)
 	/* alloc & init field type info */
 	space->max_fieldno = max_fieldno;
 	space->field_types = (enum field_type *)
-			     calloc(max_fieldno, sizeof(enum field_type));
+			     calloc(max_fieldno + 1, sizeof(enum field_type));
 
 	/* extract field type info */
 	for (i = 0; i < key_count; i++) {
 		struct key_def *def = &key_defs[i];
 		for (uint32_t pi = 0; pi < def->part_count; pi++) {
 			struct key_part *part = &def->parts[pi];
-			assert(part->fieldno < max_fieldno);
+			assert(part->fieldno <= max_fieldno);
 			space->field_types[part->fieldno] = part->type;
 		}
 	}