diff --git a/build.py b/build.py
index cca49a90a8..d55a6edef1 100755
--- a/build.py
+++ b/build.py
@@ -258,6 +258,10 @@ def examples_star_json(name, match):
             "examples/%(id)s.js" % match.groupdict()],
           "compile": {
             "js": [
+              # When compling the examples, the OpenLayers 'externs' can be used
+              # as inputs directly. By passing them directly to the compiler,
+              # they are handled like source code (as manage_closure_dependencies
+              # prevents them from being ignored by the compiler).
               "externs/olx.js",
               "externs/oli.js",
             ],