diff --git a/lib/less/parser/parser.js b/lib/less/parser/parser.js
index 2e631c15f..80f7c525e 100644
--- a/lib/less/parser/parser.js
+++ b/lib/less/parser/parser.js
@@ -814,7 +814,7 @@ var Parser = function Parser(context, imports, fileInfo) {
                         if (!e) {
                             break;
                         }
-                        elem = new(tree.Element)(c, e, elemIndex, fileInfo);
+                        elem = new(tree.Element)(c, e, false, elemIndex, fileInfo);
                         if (elements) {
                             elements.push(elem);
                         } else {
@@ -1101,7 +1101,7 @@ var Parser = function Parser(context, imports, fileInfo) {
                     }
                 }
 
-                if (e) { return new(tree.Element)(c, e, index, fileInfo); }
+                if (e) { return new(tree.Element)(c, e, e instanceof tree.Variable, index, fileInfo); }
             },
 
             //
@@ -1181,6 +1181,30 @@ var Parser = function Parser(context, imports, fileInfo) {
                 if (elements) { return new(tree.Selector)(elements, allExtends, condition, index, fileInfo); }
                 if (allExtends) { error('Extend must be used to extend a selector, it cannot be used on its own'); }
             },
+            selectors: function () {
+                var s, selectors;
+                while (true) {
+                    s = this.selector();
+                    if (!s) {
+                        break;
+                    }
+                    if (selectors) {
+                        selectors.push(s);
+                    } else {
+                        selectors = [ s ];
+                    }
+                    parserInput.commentStore.length = 0;
+                    if (s.condition && selectors.length > 1) {
+                        error("Guards are only currently allowed on a single selector.");
+                    }
+                    if (!parserInput.$char(',')) { break; }
+                    if (s.condition) {
+                        error("Guards are only currently allowed on a single selector.");
+                    }
+                    parserInput.commentStore.length = 0;
+                }
+                return selectors;
+            },
             attribute: function () {
                 if (!parserInput.$char('[')) { return; }
 
@@ -1232,7 +1256,7 @@ var Parser = function Parser(context, imports, fileInfo) {
             // div, .class, body > p {...}
             //
             ruleset: function () {
-                var selectors, s, rules, debugInfo;
+                var selectors, rules, debugInfo;
 
                 parserInput.save();
 
@@ -1240,26 +1264,7 @@ var Parser = function Parser(context, imports, fileInfo) {
                     debugInfo = getDebugInfo(parserInput.i);
                 }
 
-                while (true) {
-                    s = this.selector();
-                    if (!s) {
-                        break;
-                    }
-                    if (selectors) {
-                        selectors.push(s);
-                    } else {
-                        selectors = [ s ];
-                    }
-                    parserInput.commentStore.length = 0;
-                    if (s.condition && selectors.length > 1) {
-                        error('Guards are only currently allowed on a single selector.');
-                    }
-                    if (!parserInput.$char(',')) { break; }
-                    if (s.condition) {
-                        error('Guards are only currently allowed on a single selector.');
-                    }
-                    parserInput.commentStore.length = 0;
-                }
+                selectors = this.selectors();
 
                 if (selectors && (rules = this.block())) {
                     parserInput.forget();
diff --git a/lib/less/tree/element.js b/lib/less/tree/element.js
index 371d25565..13fa3b2ba 100644
--- a/lib/less/tree/element.js
+++ b/lib/less/tree/element.js
@@ -2,7 +2,7 @@ var Node = require('./node'),
     Paren = require('./paren'),
     Combinator = require('./combinator');
 
-var Element = function (combinator, value, index, currentFileInfo, visibilityInfo) {
+var Element = function (combinator, value, isVariable, index, currentFileInfo, visibilityInfo) {
     this.combinator = combinator instanceof Combinator ?
                       combinator : new Combinator(combinator);
 
@@ -13,6 +13,7 @@ var Element = function (combinator, value, index, currentFileInfo, visibilityInf
     } else {
         this.value = '';
     }
+    this.isVariable = isVariable;
     this._index = index;
     this._fileInfo = currentFileInfo;
     this.copyVisibilityInfo(visibilityInfo);
@@ -30,12 +31,14 @@ Element.prototype.accept = function (visitor) {
 Element.prototype.eval = function (context) {
     return new Element(this.combinator,
                              this.value.eval ? this.value.eval(context) : this.value,
+                             this.isVariable,
                              this.getIndex(),
                              this.fileInfo(), this.visibilityInfo());
 };
 Element.prototype.clone = function () {
     return new Element(this.combinator,
         this.value,
+        this.isVariable,
         this.getIndex(),
         this.fileInfo(), this.visibilityInfo());
 };
diff --git a/lib/less/tree/mixin-definition.js b/lib/less/tree/mixin-definition.js
index b73bf5362..9b38258df 100644
--- a/lib/less/tree/mixin-definition.js
+++ b/lib/less/tree/mixin-definition.js
@@ -8,7 +8,7 @@ var Selector = require('./selector'),
 
 var Definition = function (name, params, rules, condition, variadic, frames, visibilityInfo) {
     this.name = name;
-    this.selectors = [new Selector([new Element(null, name, this._index, this._fileInfo)])];
+    this.selectors = [new Selector([new Element(null, name, false, this._index, this._fileInfo)])];
     this.params = params;
     this.condition = condition;
     this.variadic = variadic;
diff --git a/lib/less/tree/ruleset.js b/lib/less/tree/ruleset.js
index 0b83520ef..66304c663 100644
--- a/lib/less/tree/ruleset.js
+++ b/lib/less/tree/ruleset.js
@@ -41,22 +41,47 @@ Ruleset.prototype.accept = function (visitor) {
     }
 };
 Ruleset.prototype.eval = function (context) {
-    var thisSelectors = this.selectors, selectors,
-        selCnt, selector, i, hasOnePassingSelector = false;
+    var that = this, selectors, selCnt, selector, i, hasVariable, hasOnePassingSelector = false;
 
-    if (thisSelectors && (selCnt = thisSelectors.length)) {
+    if (this.selectors && (selCnt = this.selectors.length)) {
         selectors = new Array(selCnt);
         defaultFunc.error({
             type: 'Syntax',
             message: 'it is currently only allowed in parametric mixin guards,'
         });
+
         for (i = 0; i < selCnt; i++) {
-            selector = thisSelectors[i].eval(context);
+            selector = this.selectors[i].eval(context);
+            for (var j = 0; j < selector.elements.length; j++) {
+                if (selector.elements[j].isVariable) {
+                    hasVariable = true;
+                    break;
+                }
+            }
             selectors[i] = selector;
             if (selector.evaldCondition) {
                 hasOnePassingSelector = true;
             }
         }
+
+        if (hasVariable) {
+            var toParseSelectors = new Array(selCnt);
+            for (i = 0; i < selCnt; i++) {
+                selector = selectors[i];
+                toParseSelectors[i] = selector.toCSS(context);
+            }
+            this.parse.parseNode(
+                toParseSelectors.join(','),
+                ["selectors"], 
+                selectors[0].getIndex(), 
+                selectors[0].fileInfo(), 
+                function(err, result) {
+                    if (result) {
+                        selectors = utils.flattenArray(result);
+                    }
+                });
+        }
+
         defaultFunc.reset();
     } else {
         hasOnePassingSelector = true;
@@ -162,7 +187,7 @@ Ruleset.prototype.eval = function (context) {
         // for rulesets, check if it is a css guard and can be removed
         if (rule instanceof Ruleset && rule.selectors && rule.selectors.length === 1) {
             // check if it can be folded in (e.g. & where)
-            if (rule.selectors[0].isJustParentSelector()) {
+            if (rule.selectors[0] && rule.selectors[0].isJustParentSelector()) {
                 rsRules.splice(i--, 1);
 
                 for (var j = 0; (subRule = rule.rules[j]); j++) {
@@ -511,7 +536,13 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
         } else {
             var insideParent = new Array(elementsToPak.length);
             for (j = 0; j < elementsToPak.length; j++) {
-                insideParent[j] = new Element(null, elementsToPak[j], originalElement._index, originalElement._fileInfo);
+                insideParent[j] = new Element(
+                    null,
+                    elementsToPak[j],
+                    originalElement.isVariable,
+                    originalElement._index,
+                    originalElement._fileInfo
+                );
             }
             replacementParen = new Paren(new Selector(insideParent));
         }
@@ -520,7 +551,7 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
 
     function createSelector(containedElement, originalElement) {
         var element, selector;
-        element = new Element(null, containedElement, originalElement._index, originalElement._fileInfo);
+        element = new Element(null, containedElement, originalElement.isVariable, originalElement._index, originalElement._fileInfo);
         selector = new Selector([element]);
         return selector;
     }
@@ -545,7 +576,8 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
         }
 
         if (addPath.length > 0) {
-            // /deep/ is a combinator that is valid without anything in front of it
+            // /deep/ is a CSS4 selector - (removed, so should deprecate)
+            // that is valid without anything in front of it
             // so if the & does not have a combinator that is "" or " " then
             // and there is a combinator on the parent, then grab that.
             // this also allows + a { & .b { .a & { ... though not sure why you would want to do that
@@ -554,7 +586,13 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
                 combinator = parentEl.combinator;
             }
             // join the elements so far with the first part of the parent
-            newJoinedSelector.elements.push(new Element(combinator, parentEl.value, replacedElement._index, replacedElement._fileInfo));
+            newJoinedSelector.elements.push(new Element(
+                combinator,
+                parentEl.value,
+                replacedElement.isVariable,
+                replacedElement._index,
+                replacedElement._fileInfo
+            ));
             newJoinedSelector.elements = newJoinedSelector.elements.concat(addPath[0].elements.slice(1));
         }
 
@@ -688,7 +726,7 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
                         // the combinator used on el should now be applied to the next element instead so that
                         // it is not lost
                         if (sel.length > 0) {
-                            sel[0].elements.push(new Element(el.combinator, '', el._index, el._fileInfo));
+                            sel[0].elements.push(new Element(el.combinator, '', el.isVariable, el._index, el._fileInfo));
                         }
                         selectorsMultiplied.push(sel);
                     }
diff --git a/lib/less/tree/selector.js b/lib/less/tree/selector.js
index 1486049b4..18808a356 100644
--- a/lib/less/tree/selector.js
+++ b/lib/less/tree/selector.js
@@ -54,7 +54,7 @@ Selector.prototype.getElements = function(els) {
     return els;
 };
 Selector.prototype.createEmptySelectors = function() {
-    var el = new Element('', '&', this._index, this._fileInfo),
+    var el = new Element('', '&', false, this._index, this._fileInfo),
         sels = [new Selector([el], null, null, this._index, this._fileInfo)];
     sels[0].mediaEmpty = true;
     return sels;
diff --git a/lib/less/utils.js b/lib/less/utils.js
index 185b9a37e..1c830e7c8 100644
--- a/lib/less/utils.js
+++ b/lib/less/utils.js
@@ -1,5 +1,5 @@
 /* jshint proto: true */
-module.exports = {
+var utils = {
     getLocation: function(index, inputStream) {
         var n = index + 1,
             line = null,
@@ -65,5 +65,21 @@ module.exports = {
             }
         }
         return obj1;
+    },
+    flattenArray: function(arr, result) {
+        result = result || [];
+        for (var i = 0, length = arr.length; i < length; i++) {
+            var value = arr[i];
+            if (Array.isArray(value)) {
+                utils.flattenArray(value, result);
+            } else {
+                if (value !== undefined) {
+                    result.push(value);
+                }
+            }
+        }
+        return result;
     }
 };
+
+module.exports = utils;
\ No newline at end of file
diff --git a/lib/less/visitors/extend-visitor.js b/lib/less/visitors/extend-visitor.js
index d8f7c17f3..be13f8242 100644
--- a/lib/less/visitors/extend-visitor.js
+++ b/lib/less/visitors/extend-visitor.js
@@ -385,6 +385,7 @@ ProcessExtendsVisitor.prototype = {
             firstElement = new tree.Element(
                 match.initialCombinator,
                 replacementSelector.elements[0].value,
+                replacementSelector.elements[0].isVariable,
                 replacementSelector.elements[0].getIndex(),
                 replacementSelector.elements[0].fileInfo()
             );
diff --git a/test/css/parse-interpolation.css b/test/css/parse-interpolation.css
new file mode 100644
index 000000000..21122d72e
--- /dev/null
+++ b/test/css/parse-interpolation.css
@@ -0,0 +1,36 @@
+input[type=text]:focus,
+input[type=email]:focus,
+input[type=password]:focus,
+textarea:focus {
+  foo: bar;
+}
+.a + .z,
+.b + .z,
+.c + .z {
+  color: blue;
+}
+.bar .d.a,
+.bar .b,
+.c.bar:hover,
+.bar baz {
+  color: blue;
+}
+.a + .e,
+.b.c + .e,
+.d + .e {
+  foo: bar;
+}
+input[class="text"],
+input.text {
+  background: red;
+}
+.master-page-1 .selector-1,
+.master-page-1 .selector-2 {
+  background-color: red;
+}
+.fruit-apple,
+.fruit-satsuma,
+.fruit-banana,
+.fruit-pear {
+  content: "Just a test.";
+}
diff --git a/test/css/permissive-parse.css b/test/css/permissive-parse.css
index 1ed0773d4..f5f498afd 100644
--- a/test/css/permissive-parse.css
+++ b/test/css/permissive-parse.css
@@ -21,7 +21,9 @@
 @-moz-whatever (foo: "(" bam ")") {
   bar: foo;
 }
-#selector, .bar, foo[attr="blah"] {
+#selector,
+.bar,
+foo[attr="blah"] {
   bar: value;
 }
 @media (min-width: 640px) {
diff --git a/test/less/parse-interpolation.less b/test/less/parse-interpolation.less
new file mode 100644
index 000000000..9c9c7afca
--- /dev/null
+++ b/test/less/parse-interpolation.less
@@ -0,0 +1,53 @@
+@inputs: input[type=text], input[type=email], input[type=password], textarea;
+
+@{inputs} {
+  &:focus {
+    foo: bar;
+  }
+} 
+
+@classes: .a, .b, .c;
+
+@{classes} {  
+  + .z {
+    color: blue; 
+  }
+}
+
+.bar {
+  .d@{classes}&:hover, baz {
+    color: blue;
+  }
+}
+
+@c: ~'.a, .b';
+@d: ~'.c, .d';
+@e: ~' + .e';
+
+@{c}@{d} {
+  @{e} {
+    foo: bar;
+  }
+}
+
+@textClasses: ~'&[class="text"], &.text';
+
+input {
+  @{textClasses} {
+    background: red;
+  }
+}
+
+@my-selector: ~'.selector-1, .selector-2';
+.master-page-1 {
+    @{my-selector} {
+        background-color: red;
+    }
+}
+
+@list: apple, satsuma, banana, pear;
+@{list} {
+  .fruit-& {
+    content: "Just a test.";
+  }
+}
\ No newline at end of file