diff --git a/core/generator.js b/core/generator.js
index fe1bd6eb5..c2cf50988 100644
--- a/core/generator.js
+++ b/core/generator.js
@@ -159,6 +159,7 @@ Blockly.Generator.prototype.allNestedComments = function(block) {
 
 /**
  * Generate code for the specified block (and attached blocks).
+ * The generator should be initialized before calling this function.
  * @param {Blockly.Block} block The block to generate code for.
  * @param {boolean=} opt_thisOnly True to generate code for only this statement.
  * @return {string|!Array} For statement blocks, the generated code.