diff --git a/spec/parser/javascript/charset_range_spec.js b/spec/parser/javascript/charset_range_spec.js
index 40420df..329524e 100644
--- a/spec/parser/javascript/charset_range_spec.js
+++ b/spec/parser/javascript/charset_range_spec.js
@@ -17,6 +17,13 @@ describe('parser/javascript/charset_range.js', function() {
     }));
   });
 
+  it('throws an exception when the range is out of order', function() {
+    var parser = new javascript.Parser('z-a');
+    expect(() => {
+      parser.__consume__charset_range();
+    }).toThrow('Range out of order in character class: z-a');
+  });
+
   describe('#_render', function() {
 
     beforeEach(function() {
diff --git a/src/js/parser/javascript/charset_range.js b/src/js/parser/javascript/charset_range.js
index 2b69d1b..cbc0dd2 100644
--- a/src/js/parser/javascript/charset_range.js
+++ b/src/js/parser/javascript/charset_range.js
@@ -26,5 +26,9 @@ export default {
   setup() {
     this.first = this.properties.first;
     this.last = this.properties.last;
+
+    if (this.first.ordinal > this.last.ordinal) {
+      throw `Range out of order in character class: ${this.textValue}`;
+    }
   }
 };