diff --git a/src/fontra_compile/builder.py b/src/fontra_compile/builder.py
index 334d642..217357b 100644
--- a/src/fontra_compile/builder.py
+++ b/src/fontra_compile/builder.py
@@ -454,6 +454,8 @@ def buildVARC(self, axisTags):
                 components.append(compo)
 
             if self.glyphInfos[glyphName].glyph.numberOfContours:
+                # Add a component for the outline section, so we can effectively
+                # mix outlines and components. This is a special case in the spec.
                 compo = ot.VarComponent()
                 compo.glyphName = glyphName
                 components.append(compo)