diff --git a/lib/less/tree/unit.js b/lib/less/tree/unit.js
index 0b8441df..21d7cd75 100644
--- a/lib/less/tree/unit.js
+++ b/lib/less/tree/unit.js
@@ -23,6 +23,8 @@ Unit.prototype.genCSS = function (context, output) {
         output.add(this.numerator[0]); // the ideal situation
     } else if (!strictUnits && this.backupUnit) {
         output.add(this.backupUnit);
+    } else if (!strictUnits && this.denominator.length) {
+        output.add(this.denominator[0]);
     }
 };
 Unit.prototype.toString = function () {