diff --git a/lib/compiler/passes/report-left-recursion.js b/lib/compiler/passes/report-left-recursion.js
index 1c6a7d9..5c8592d 100644
--- a/lib/compiler/passes/report-left-recursion.js
+++ b/lib/compiler/passes/report-left-recursion.js
@@ -1,4 +1,5 @@
-var utils = require("../../utils");
+var utils        = require("../../utils"),
+    GrammarError = require("../../grammar-error.js");
 
 /* Checks that no left recursion is present. */
 module.exports = function(ast) {
@@ -48,7 +49,7 @@ module.exports = function(ast) {
     rule_ref:
       function(node, appliedRules) {
         if (utils.contains(appliedRules, node.name)) {
-          throw new PEG.GrammarError(
+          throw new GrammarError(
             "Left recursion detected for rule \"" + node.name + "\"."
           );
         }
diff --git a/lib/compiler/passes/report-missing-rules.js b/lib/compiler/passes/report-missing-rules.js
index f600862..c1193bc 100644
--- a/lib/compiler/passes/report-missing-rules.js
+++ b/lib/compiler/passes/report-missing-rules.js
@@ -1,4 +1,5 @@
-var utils = require("../../utils");
+var utils        = require("../../utils"),
+    GrammarError = require("../../grammar-error.js");
 
 /* Checks that all referenced rules exist. */
 module.exports = function(ast) {
@@ -30,7 +31,7 @@ module.exports = function(ast) {
     rule_ref:
       function(node) {
         if (!utils.findRuleByName(ast, node.name)) {
-          throw new PEG.GrammarError(
+          throw new GrammarError(
             "Referenced rule \"" + node.name + "\" does not exist."
           );
         }