diff --git a/lib/compiler/passes/report-undefined-rules.js b/lib/compiler/passes/report-undefined-rules.js
index 798568e..e6a9b8e 100644
--- a/lib/compiler/passes/report-undefined-rules.js
+++ b/lib/compiler/passes/report-undefined-rules.js
@@ -24,19 +24,15 @@ function reportUndefinedRules( ast, options ) {
 
     check( ast );
 
-    if ( options.allowedStartRules ) {
+    options.allowedStartRules.forEach( rule => {
 
-        options.allowedStartRules.forEach( rule => {
+        if ( ! asts.findRule( ast, rule ) ) {
 
-            if ( ! asts.findRule( ast, rule ) ) {
+            throw new GrammarError( `Start rule "${ rule }" is not defined.` );
 
-                throw new GrammarError( `Start rule "${ rule }" is not defined.` );
-
-            }
-
-        } );
+        }
 
-    }
+    } );
 
 }
 
diff --git a/test/spec/unit/compiler/passes/helpers.js b/test/spec/unit/compiler/passes/helpers.js
index 86f37e1..d897108 100644
--- a/test/spec/unit/compiler/passes/helpers.js
+++ b/test/spec/unit/compiler/passes/helpers.js
@@ -55,6 +55,14 @@ module.exports = function ( chai, utils ) {
 
         const ast = parser.parse( grammar );
 
+        if ( ! options.allowedStartRules ) {
+
+            options.allowedStartRules = ast.rules.length > 0
+                ? [ ast.rules[ 0 ].name ]
+                : [];
+
+        }
+
         utils.flag( this, "object" )( ast, options );
 
         this.assert(
@@ -73,6 +81,14 @@ module.exports = function ( chai, utils ) {
 
         const ast = parser.parse( grammar );
 
+        if ( ! options.allowedStartRules ) {
+
+            options.allowedStartRules = ast.rules.length > 0
+                ? [ ast.rules[ 0 ].name ]
+                : [];
+
+        }
+
         let passed, result;
 
         try {