diff --git a/core/generator.js b/core/generator.js
index b375b7a06..b9b488d5c 100644
--- a/core/generator.js
+++ b/core/generator.js
@@ -77,6 +77,15 @@ Blockly.Generator.prototype.COMMENT_WRAP = 60;
  */
 Blockly.Generator.prototype.ORDER_OVERRIDES = [];
 
+/**
+ * Whether the init method has been called.
+ * Generators that set this flag to false after creation and true in init
+ * will cause blockToCode to emit a warning if the generator has not been
+ * initialized. If this flag is untouched, it will have no effect.
+ * @type {?boolean}
+ */
+Blockly.Generator.prototype.isInitialized = null;
+
 /**
  * Generate code for all blocks in the workspace to the specified language.
  * @param {Blockly.Workspace} workspace Workspace to generate code from.
@@ -167,6 +176,10 @@ Blockly.Generator.prototype.allNestedComments = function(block) {
  *     operator order value.  Returns '' if block is null.
  */
 Blockly.Generator.prototype.blockToCode = function(block, opt_thisOnly) {
+  if (this.isInitialized === false) {
+    console.warn(
+        'Generator init was not called before blockToCode was called.');
+  }
   if (!block) {
     return '';
   }
diff --git a/generators/dart.js b/generators/dart.js
index 1b276ddf8..a801a0655 100644
--- a/generators/dart.js
+++ b/generators/dart.js
@@ -71,6 +71,12 @@ Blockly.Dart.ORDER_CASCADE = 15;       // ..
 Blockly.Dart.ORDER_ASSIGNMENT = 16;    // = *= /= ~/= %= += -= <<= >>= &= ^= |=
 Blockly.Dart.ORDER_NONE = 99;          // (...)
 
+/**
+ * Whether the init method has been called.
+ * @type {?boolean}
+ */
+Blockly.Dart.isInitialized = false;
+
 /**
  * Initialise the database of variable names.
  * @param {!Blockly.Workspace} workspace Workspace to generate code from.
@@ -111,6 +117,7 @@ Blockly.Dart.init = function(workspace) {
     Blockly.Dart.definitions_['variables'] =
         'var ' + defvars.join(', ') + ';';
   }
+  this.isInitialized = true;
 };
 
 /**
diff --git a/generators/javascript.js b/generators/javascript.js
index 630fd4786..368a35a6d 100644
--- a/generators/javascript.js
+++ b/generators/javascript.js
@@ -113,6 +113,12 @@ Blockly.JavaScript.ORDER_OVERRIDES = [
   [Blockly.JavaScript.ORDER_LOGICAL_OR, Blockly.JavaScript.ORDER_LOGICAL_OR]
 ];
 
+/**
+ * Whether the init method has been called.
+ * @type {?boolean}
+ */
+Blockly.JavaScript.isInitialized = false;
+
 /**
  * Initialise the database of variable names.
  * @param {!Blockly.Workspace} workspace Workspace to generate code from.
@@ -153,6 +159,7 @@ Blockly.JavaScript.init = function(workspace) {
     Blockly.JavaScript.definitions_['variables'] =
         'var ' + defvars.join(', ') + ';';
   }
+  this.isInitialized = true;
 };
 
 /**
diff --git a/generators/lua.js b/generators/lua.js
index fa16b8182..75a6b7b8b 100644
--- a/generators/lua.js
+++ b/generators/lua.js
@@ -79,6 +79,12 @@ Blockly.Lua.ORDER_NONE = 99;
  * option used for lists and text.
  */
 
+/**
+ * Whether the init method has been called.
+ * @type {?boolean}
+ */
+Blockly.Lua.isInitialized = false;
+
 /**
  * Initialise the database of variable names.
  * @param {!Blockly.Workspace} workspace Workspace to generate code from.
@@ -97,6 +103,7 @@ Blockly.Lua.init = function(workspace) {
     Blockly.Lua.variableDB_.reset();
   }
   Blockly.Lua.variableDB_.setVariableMap(workspace.getVariableMap());
+  this.isInitialized = true;
 };
 
 /**
diff --git a/generators/php.js b/generators/php.js
index 0b96b5b21..326cc8ecd 100644
--- a/generators/php.js
+++ b/generators/php.js
@@ -117,6 +117,12 @@ Blockly.PHP.ORDER_OVERRIDES = [
   [Blockly.PHP.ORDER_LOGICAL_OR, Blockly.PHP.ORDER_LOGICAL_OR]
 ];
 
+/**
+ * Whether the init method has been called.
+ * @type {?boolean}
+ */
+Blockly.PHP.isInitialized = false;
+
 /**
  * Initialise the database of variable names.
  * @param {!Blockly.Workspace} workspace Workspace to generate code from.
@@ -154,6 +160,7 @@ Blockly.PHP.init = function(workspace) {
 
   // Declare all of the variables.
   Blockly.PHP.definitions_['variables'] = defvars.join('\n');
+  this.isInitialized = true;
 };
 
 /**
diff --git a/generators/python.js b/generators/python.js
index e6191e52e..9844b9501 100644
--- a/generators/python.js
+++ b/generators/python.js
@@ -125,6 +125,12 @@ Blockly.Python.ORDER_OVERRIDES = [
   [Blockly.Python.ORDER_LOGICAL_OR, Blockly.Python.ORDER_LOGICAL_OR]
 ];
 
+/**
+ * Whether the init method has been called.
+ * @type {?boolean}
+ */
+Blockly.Python.isInitialized = false;
+
 /**
  * Initialise the database of variable names.
  * @param {!Blockly.Workspace} workspace Workspace to generate code from.
@@ -166,6 +172,7 @@ Blockly.Python.init = function(workspace) {
   }
 
   Blockly.Python.definitions_['variables'] = defvars.join('\n');
+  this.isInitialized = true;
 };
 
 /**