diff --git a/src/ast/variable.h b/src/ast/variable.h
index 3ef3b8a..bc0b8e8 100644
--- a/src/ast/variable.h
+++ b/src/ast/variable.h
@@ -135,7 +135,9 @@
   /// The variable symbol
   const Symbol symbol;
 
-  /// The variable type
+  /// The declared variable type. This is null if the type is inferred, e.g.:
+  ///   let f = 1.0;
+  ///   var i = 1;
   const ast::Type* const type;
 
   /// True if this is a constant, false otherwise