diff --git a/lib/compiler/index.js b/lib/compiler/index.js
index d9888fd..502f2d3 100644
--- a/lib/compiler/index.js
+++ b/lib/compiler/index.js
@@ -19,7 +19,7 @@ var compiler = {
    */
   passes: {
     check: {
-      reportMissingRules:    require("./passes/report-missing-rules"),
+      reportUndefinedRules:  require("./passes/report-undefined-rules"),
       reportDuplicateRules:  require("./passes/report-duplicate-rules"),
       reportDuplicateLabels: require("./passes/report-duplicate-labels"),
       reportLeftRecursion:   require("./passes/report-left-recursion"),
diff --git a/lib/compiler/passes/report-missing-rules.js b/lib/compiler/passes/report-undefined-rules.js
similarity index 85%
rename from lib/compiler/passes/report-missing-rules.js
rename to lib/compiler/passes/report-undefined-rules.js
index 8a7a46e..c71b03f 100644
--- a/lib/compiler/passes/report-missing-rules.js
+++ b/lib/compiler/passes/report-undefined-rules.js
@@ -5,7 +5,7 @@ var GrammarError = require("../../grammar-error"),
     visitor      = require("../visitor");
 
 /* Checks that all referenced rules exist. */
-function reportMissingRules(ast) {
+function reportUndefinedRules(ast) {
   var check = visitor.build({
     rule_ref: function(node) {
       if (!asts.findRule(ast, node.name)) {
@@ -20,4 +20,4 @@ function reportMissingRules(ast) {
   check(ast);
 }
 
-module.exports = reportMissingRules;
+module.exports = reportUndefinedRules;
diff --git a/package.json b/package.json
index fad938a..2df73c0 100644
--- a/package.json
+++ b/package.json
@@ -31,7 +31,7 @@
     "lib/compiler/passes/report-duplicate-labels.js",
     "lib/compiler/passes/report-infinite-loops.js",
     "lib/compiler/passes/report-left-recursion.js",
-    "lib/compiler/passes/report-missing-rules.js",
+    "lib/compiler/passes/report-undefined-rules.js",
     "lib/compiler/visitor.js",
     "lib/grammar-error.js",
     "lib/parser.js",
diff --git a/spec/api/pegjs-api.spec.js b/spec/api/pegjs-api.spec.js
index caf82d2..5448f12 100644
--- a/spec/api/pegjs-api.spec.js
+++ b/spec/api/pegjs-api.spec.js
@@ -16,7 +16,7 @@ describe("PEG.js API", function() {
     });
 
     it("throws an exception on semantic error", function() {
-      expect(function() { peg.generate('start = missing'); }).toThrow();
+      expect(function() { peg.generate('start = undefined'); }).toThrow();
     });
 
     describe("allowed start rules", function() {
diff --git a/spec/index.html b/spec/index.html
index cc4cb88..321bd49 100644
--- a/spec/index.html
+++ b/spec/index.html
@@ -9,7 +9,7 @@
     <script src="helpers.js"></script>
     <script src="unit/parser.spec.js"></script>
     <script src="unit/compiler/passes/helpers.js"></script>
-    <script src="unit/compiler/passes/report-missing-rules.spec.js"></script>
+    <script src="unit/compiler/passes/report-undefined-rules.spec.js"></script>
     <script src="unit/compiler/passes/report-duplicate-rules.spec.js"></script>
     <script src="unit/compiler/passes/report-duplicate-labels.spec.js"></script>
     <script src="unit/compiler/passes/report-left-recursion.spec.js"></script>
diff --git a/spec/unit/compiler/passes/report-missing-rules.spec.js b/spec/unit/compiler/passes/report-missing-rules.spec.js
deleted file mode 100644
index 00b2cff..0000000
--- a/spec/unit/compiler/passes/report-missing-rules.spec.js
+++ /dev/null
@@ -1,17 +0,0 @@
-/* global peg */
-
-"use strict";
-
-describe("compiler pass |reportMissingRules|", function() {
-  var pass = peg.compiler.passes.check.reportMissingRules;
-
-  it("reports missing rules", function() {
-    expect(pass).toReportError('start = missing', {
-      message:  'Rule "missing" is not defined.',
-      location: {
-        start: { offset:  8, line: 1, column:  9 },
-        end:   { offset: 15, line: 1, column: 16 }
-      }
-    });
-  });
-});
diff --git a/spec/unit/compiler/passes/report-undefined-rules.spec.js b/spec/unit/compiler/passes/report-undefined-rules.spec.js
new file mode 100644
index 0000000..bf9c5b5
--- /dev/null
+++ b/spec/unit/compiler/passes/report-undefined-rules.spec.js
@@ -0,0 +1,17 @@
+/* global peg */
+
+"use strict";
+
+describe("compiler pass |reportUndefinedRules|", function() {
+  var pass = peg.compiler.passes.check.reportUndefinedRules;
+
+  it("reports undefined rules", function() {
+    expect(pass).toReportError('start = undefined', {
+      message:  'Rule "undefined" is not defined.',
+      location: {
+        start: { offset:  8, line: 1, column:  9 },
+        end:   { offset: 17, line: 1, column: 18 }
+      }
+    });
+  });
+});