diff --git a/common.c b/common.c
index 548de33..0981ed5 100644
--- a/common.c
+++ b/common.c
@@ -534,7 +534,7 @@ struct config_schema
 	bool (*validate) (struct config_item_ *, const struct config_item_ *);
 
 	/// The value has changed. Only appliable to objects.
-	bool (*on_changed) (struct config_item_ *);
+	void (*on_changed) (struct config_item_ *);
 
 	/// Free any resources located in "item->user_data"
 	void (*on_destroy) (struct config_item_ *item);
@@ -542,12 +542,33 @@ struct config_schema
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-static void
-config_item_destroy (struct config_item_ *self)
+static const char *
+config_item_type_name (enum config_item_type type)
 {
-	if (self->schema && self->schema->on_destroy)
-		self->schema->on_destroy (self);
+	switch (type)
+	{
+	case CONFIG_ITEM_NULL:          return "null";
+	case CONFIG_ITEM_BOOLEAN:       return "boolean";
+	case CONFIG_ITEM_INTEGER:       return "integer";
+	case CONFIG_ITEM_STRING:        return "string";
+	case CONFIG_ITEM_STRING_ARRAY:  return "string array";
 
+	default:
+		hard_assert (!"invalid config item type value");
+		return NULL;
+	}
+}
+
+static bool
+config_item_type_is_string (enum config_item_type type)
+{
+	return type == CONFIG_ITEM_STRING
+		|| type == CONFIG_ITEM_STRING_ARRAY;
+}
+
+static void
+config_item_free (struct config_item_ *self)
+{
 	switch (self->type)
 	{
 	case CONFIG_ITEM_STRING:
@@ -559,9 +580,32 @@ config_item_destroy (struct config_item_ *self)
 	default:
 		break;
 	}
+}
+
+static void
+config_item_destroy (struct config_item_ *self)
+{
+	if (self->schema && self->schema->on_destroy)
+		self->schema->on_destroy (self);
+
+	config_item_free (self);
 	free (self);
 }
 
+/// Doesn't do any validations or handle schemas, just moves source data
+/// to the target item and destroys the source item
+static void
+config_item_move (struct config_item_ *self, struct config_item_ *source)
+{
+	// Not quite sure how to handle that
+	hard_assert (!source->schema);
+
+	config_item_free (self);
+	self->type = source->type;
+	memcpy (&self->value, &source->value, sizeof source->value);
+	free (source);
+}
+
 static struct config_item_ *
 config_item_new (enum config_item_type type)
 {
@@ -618,19 +662,59 @@ config_item_object (void)
 	return self;
 }
 
-/// Doesn't do any validations or such, only moves source data to the item
-static void
-config_item_move (struct config_item_ *self, struct config_item_ *source)
+static bool
+config_schema_accepts_type
+	(struct config_schema *self, enum config_item_type type)
 {
-	// TODO
+	if (self->type == type)
+		return true;
+	// This is a bit messy but it has its purpose
+	if (config_item_type_is_string (self->type)
+	 && config_item_type_is_string (type))
+		return true;
+	return self->is_nullable && type == CONFIG_ITEM_NULL;
+
 }
 
 static bool
-config_item_set_from (struct config_item_ *self,
-	struct config_item_ *source, struct error **e)
+config_item_set_from (struct config_item_ *self, struct config_item_ *source,
+	struct error **e)
 {
-	hard_assert (self->type == CONFIG_ITEM_OBJECT);
-	// TODO
+	struct config_schema *schema = self->schema;
+	if (!schema)
+	{
+		// Easy, we don't know what this item is
+		config_item_move (self, source);
+		return true;
+	}
+
+	// Otherwise we check the type and validate the item
+	if (!config_schema_accepts_type (schema, source->type))
+	{
+		error_set (e, "invalid type of value, expected: %s%s",
+			config_item_type_name (schema->type),
+			schema->is_nullable ? " (or null)" : "");
+		return false;
+	}
+
+	if (schema->validate && !schema->validate (self, source))
+	{
+		// XXX: perhaps "schema->validate" could provide a message for us?
+		error_set (e, "invalid value");
+		return false;
+	}
+
+	// Make sure the string subtype fits the schema
+	if (config_item_type_is_string (self->type)
+	 && config_item_type_is_string (source->type))
+		source->type = self->type;
+
+	config_item_move (self, source);
+
+	// Notify owner about the change so that they can apply it
+	if (schema->on_changed)
+		schema->on_changed (self);
+	return true;
 }
 
 static struct config_item_ *