diff --git a/src/lib/custom-style.html b/src/lib/custom-style.html
index 1a9a338b4c..9621cfd103 100644
--- a/src/lib/custom-style.html
+++ b/src/lib/custom-style.html
@@ -23,6 +23,9 @@
browsers without non-native Shadow DOM.
* Custom properties used by Polymer's shim for cross-scope styling
may be defined in an `custom-style`.
+* A module attribute may be specified to pull in style data from a `dom-module`
+matching the module attribute. By using `module`, style data
+can be shared between multiple `custom-style` elements.
Example:
@@ -82,6 +85,11 @@
properties: {
// module is a property so that it deserializes
+ /**
+ * Specify module to identify a `dom-module` containing style data which
+ * should be used within the `custom-style`. By using `module` style data
+ * may be shared between multiple different `custom-style` elements.
+ */
module: String
},