diff --git a/lexical.js b/lexical.js
index 4900915a3..7a981883d 100644
--- a/lexical.js
+++ b/lexical.js
@@ -6,12 +6,12 @@ var doubleQuoted = /"[^"]*"/;
 var quoteBalanced = new RegExp(`(?:${singleQuoted.source}|${doubleQuoted.source}|[^'"])*`);
 
 var number = /(?:-?\d+\.?\d*|\.?\d+)/;
-var bool = /true|false/i;
+var bool = /true|false/;
 var identifier = /[a-zA-Z_$][a-zA-Z_$0-9]*/;
 var subscript = /\[\d+\]/;
 
 var quoted = new RegExp(`(?:${singleQuoted.source}|${doubleQuoted.source})`);
-var literal = new RegExp(`(?:${quoted.source}|${bool.source}|${number.source})`, 'i');
+var literal = new RegExp(`(?:${quoted.source}|${bool.source}|${number.source})`);
 var variable = new RegExp(`${identifier.source}(?:\\.${identifier.source}|${subscript.source})*`);
 
 // range related
@@ -19,10 +19,10 @@ var rangeLimit = new RegExp(`(?:${variable.source}|${number.source})`);
 var range = new RegExp(`\\(${rangeLimit.source}\\.\\.${rangeLimit.source}\\)`);
 var rangeCapture = new RegExp(`\\((${rangeLimit.source})\\.\\.(${rangeLimit.source})\\)`);
 
-var value = new RegExp(`(?:${literal.source}|${variable.source}|${range.source})`, 'i');
+var value = new RegExp(`(?:${literal.source}|${variable.source}|${range.source})`);
 
 // hash related
-var hash = new RegExp(`(?:${identifier.source})\\s*:\\s*(?:${value.source})`, 'g');
+var hash = new RegExp(`(?:${identifier.source})\\s*:\\s*(?:${value.source})`);
 var hashCapture = new RegExp(`(${identifier.source})\\s*:\\s*(${value.source})`, 'g');
 
 var tagLine = new RegExp(`^\\s*(${identifier.source})\\s*(.*)\\s*$`);
diff --git a/tag.js b/tag.js
index 2b1a45af3..d927ceb4c 100644
--- a/tag.js
+++ b/tag.js
@@ -2,21 +2,6 @@ const lexical = require('./lexical.js');
 const Exp = require('./expression.js');
 const TokenizationError = require('./error.js').TokenizationError;
 
-var _tagInstance = {
-    render: function(scope, register) {
-        var reg = register[this.name];
-        if(!reg) reg = register[this.name] = {};
-        var obj = hash(this.token.args, scope);
-        return this.tagImpl.render(scope, obj, reg) || '';
-    },
-    parse: function(tokens){
-        if(this.tagImpl.parse){
-            this.tagImpl.parse(this.token, tokens);
-        }
-        return this;
-    }
-};
-
 function hash(markup, scope) {
     var obj = {};
     lexical.hashCapture.lastIndex = 0;
@@ -31,6 +16,27 @@ function hash(markup, scope) {
 module.exports = function() {
     var tagImpls = {};
 
+    var _tagInstance = {
+        render: function(scope, register) {
+            var reg = register[this.name];
+            if(!reg) reg = register[this.name] = {};
+            var obj = hash(this.token.args, scope);
+            return this.tagImpl.render(scope, obj, reg) || '';
+        },
+        parse: function(token, tokens){
+            this.type = 'tag';
+            this.token = token;
+            this.name = token.name;
+
+            var tagImpl = tagImpls[this.name];
+            if (!tagImpl) throw new Error(`tag ${this.name} not found`);
+            this.tagImpl = Object.create(tagImpl);
+            if(this.tagImpl.parse){
+                this.tagImpl.parse(token, tokens);
+            }
+        }
+    };
+
     function register(name, tag) {
         if (typeof tag.render !== 'function') {
             throw new Error(`expect ${name}.render to be a function`);
@@ -38,15 +44,9 @@ module.exports = function() {
         tagImpls[name] = tag;
     }
 
-    function construct(token) {
-        var tagImpl = tagImpls[token.name];
-        if (!tagImpl) throw new Error(`tag ${token.name} not found`);
-
+    function construct(token, tokens) {
         var instance = Object.create(_tagInstance);
-        instance.token = token;
-        instance.type = 'tag';
-        instance.name = token.name;
-        instance.tagImpl = Object.create(tagImpl);
+        instance.parse(token, tokens);
         return instance;
     }
 
diff --git a/tags/cycle.js b/tags/cycle.js
index c4eb08466..3ad73a606 100644
--- a/tags/cycle.js
+++ b/tags/cycle.js
@@ -20,7 +20,7 @@ module.exports = function(liquid) {
             }
 
             if (!this.candidates.length){
-                throw new Error(`illegal tag: ${tagToken.raw}`);
+                throw new Error(`empty candidates: ${tagToken.raw}`);
             }
         },
 
diff --git a/tags/unless.js b/tags/unless.js
index c1bfe5c18..988bed864 100644
--- a/tags/unless.js
+++ b/tags/unless.js
@@ -3,23 +3,11 @@ var lexical = Liquid.lexical;
 
 module.exports = function(liquid) {
     liquid.registerTag('unless', {
-
         parse: function(tagToken, remainTokens) {
-            this.branches = [];
-            this.elseTemplates = [];
-
             var p, stream = liquid.parseStream(remainTokens)
-                .onStart(x => this.branches.push({
-                    cond: tagToken.args,
-                    templates: p = []
-                }))
-                .onTag('elsif', token => {
-                    if (!this.branches[token.args]) {
-                        this.branches.push({
-                            cond: token.args,
-                            templates: p = []
-                        });
-                    }
+                .onStart(x => {
+                    p = this.templates = [];
+                    this.cond = tagToken.args;
                 })
                 .onTag('else', token => this.elseTemplates = p = [])
                 .onTag('endunless', token => stream.stop())
@@ -32,17 +20,10 @@ module.exports = function(liquid) {
         },
 
         render: function(scope, hash) {
-            for (var i = 0; i < this.branches.length; i++) {
-                var branch = this.branches[i];
-                var cond = Liquid.evalExp(branch.cond, scope);
-                cond = Liquid.isTruthy(cond);
-                if (i === 0) cond = !cond;
-                if (cond) {
-                    return liquid.renderTemplates(branch.templates, scope);
-                }
-            }
-            return liquid.renderTemplates(this.elseTemplates, scope);
+            var cond = Liquid.evalExp(this.cond, scope);
+            return Liquid.isFalsy(cond) ?
+                liquid.renderTemplates(this.templates, scope) :
+                liquid.renderTemplates(this.elseTemplates, scope);
         }
-
     });
 };
diff --git a/template.js b/template.js
index 05574ef9d..957a29b09 100644
--- a/template.js
+++ b/template.js
@@ -77,7 +77,7 @@ module.exports = function(Tag, Filter) {
 
     function parseTag(token, tokens) {
         if (token.name === 'continue' || token.name === 'break') return token;
-        return Tag.construct(token).parse(tokens);
+        return Tag.construct(token, tokens);
     }
 
     function parseOutput(str) {
diff --git a/test/tag.js b/test/tag.js
index 0a1a54928..834ec574a 100644
--- a/test/tag.js
+++ b/test/tag.js
@@ -23,7 +23,7 @@ describe('tag', function() {
                 type: 'tag',
                 value: 'foo',
                 name: 'foo'
-            });
+            }, []);
         }).to.throw(/tag foo not found/);
     });
 
@@ -52,7 +52,7 @@ describe('tag', function() {
             type: 'tag',
             value: 'foo',
             name: 'foo'
-        }).render(scope, {});
+        }, []).render(scope, {});
         expect(spy).to.have.been.called;
     });
 
@@ -68,7 +68,7 @@ describe('tag', function() {
             name: 'foo',
             args: 'aa:foo bb: arr[0] cc: 2.3'
         };
-        tag.construct(token).render(scope, {});
+        tag.construct(token, []).render(scope, {});
         expect(spy).to.have.been.calledWithMatch(scope, {
             aa: 'bar',
             bb: 2,
diff --git a/test/tags.js b/test/tags.js
index eec807fbd..c190d2f37 100644
--- a/test/tags.js
+++ b/test/tags.js
@@ -27,11 +27,13 @@ describe('tags', function() {
             emptyArray: []
         };
     });
+
     it('should support assign', function() {
         test('{% assign foo="bar" %}{{foo}}', 'bar');
         test('{% assign foo=(1..3) %}{{foo}}', '[1,2,3]');
         test('{% assign foo="a b" | capitalize | split: " " | first %}{{foo}}', 'A');
     });
+
     it('should support case', function() {
         testThrow('{% case "foo"%}', /{% case "foo"%} not closed/);
         test('{% case "foo"%}' +
@@ -69,10 +71,22 @@ describe('tags', function() {
         testThrow('{% capture = %}{%endcapture%}', /= not valid identifier/);
     });
 
+    it('should throw when for capture closed', function() {
+        testThrow('{%capture c%}{{c}}', /tag .* not closed/);
+    });
+
     it('should support for', function() {
         test('{%for c in alpha%}{{c}}{%endfor%}', 'abc');
     });
 
+    it('should throw when for not closed', function() {
+        testThrow('{%for c in alpha%}{{c}}', /tag .* not closed/);
+    });
+
+    it('should support for else', function() {
+        test('{%for c in ""%}a{%else%}b{%endfor%}', 'b');
+    });
+
     it('should support for with forloop', function() {
         src = '{%for c in alpha%}' +
             '{{forloop.first}}.{{forloop.index}}.{{forloop.index0}}.' +
@@ -117,6 +131,10 @@ describe('tags', function() {
         test(src + src + src + src, '1231');
     });
 
+    it('should throw when cycle candidates empty', function() {
+        testThrow('{%cycle%}', /empty candidates/);
+    });
+
     it('should support cycle in for block', function() {
         src = '{% for i in (1..5) %}{% cycle one, "e"%}{% endfor %}';
         test(src, '1e1e1');