Make it clear that labels need to be specified when using a category axis on a line...

diff --git a/docs/charts/line.md b/docs/charts/line.md
index f838bac0dd2e37d7d65f623a1a4082ec693219b6..a64f436cfdb6400107ea7f9fbbbbdbd43cebde8f 100644 (file)
--- a/docs/charts/line.md
+++ b/docs/charts/line.md
@@ -142,7 +142,7 @@ The `data` property of a dataset for a line chart can be passed in two formats.
 data: [20, 10]
 ```
 
-When the `data` array is an array of numbers, the x axis is generally a [category](../axes/cartesian/category.md#Category Axis). The points are placed onto the axis using their position in the array.
+When the `data` array is an array of numbers, the x axis is generally a [category](../axes/cartesian/category.md#Category Axis). The points are placed onto the axis using their position in the array. When a line chart is created with a category axis, the `labels` property of the data object must be specified.
 
 ### Point[]