diff --git a/lib/options.js b/lib/options.js
index be62d4a..1c8db3a 100644
--- a/lib/options.js
+++ b/lib/options.js
@@ -21,6 +21,8 @@ exports.canonical = function(opts) {
     assert.ok(match, 'Invalid rate: ' + opts.rate);
     canon.limit = parseInt(match[1], 10);
     canon.window = moment.duration(1, match[2]) / 1000;
+    assert.notEqual(canon.limit, 0,  'Invalid rate limit: ' + opts.rate);
+    assert.notEqual(canon.window, 0, 'Invalid rate window: ' + opts.rate);
   }
 
   // Limit + window
diff --git a/test/options.spec.js b/test/options.spec.js
index 40aa193..7ad9639 100644
--- a/test/options.spec.js
+++ b/test/options.spec.js
@@ -95,14 +95,34 @@ describe('Options', function() {
       assertRate('5000/d', 5000, 86400);
     });
 
-    it('has to be a valid rate', function() {
+    it('has to be a valid format', function() {
       (function() {
         var opts = options.canonical({
           redis: {},
           key: 'ip',
-          rate: '50 things'
+          rate: 'foobar'
         });
-      }).should.throw('Invalid rate: 50 things');
+      }).should.throw('Invalid rate: foobar');
+    });
+
+    it('has to be a valid limit', function() {
+      (function() {
+        var opts = options.canonical({
+          redis: {},
+          key: 'ip',
+          rate: '0/hour'
+        });
+      }).should.throw('Invalid rate limit: 0/hour');
+    });
+
+    it('has to be a valid unit', function() {
+      (function() {
+        var opts = options.canonical({
+          redis: {},
+          key: 'ip',
+          rate: '50/century'
+        });
+      }).should.throw('Invalid rate window: 50/century');
     });
 
   });