diff --git a/CHANGELOG.md b/CHANGELOG.md
index ebec3d3c..59ac3f3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## next
 
+- Trim Custom Property values when possible (#393)
 - Fixed removing unit for zero-length dimentions in `min()`, `max()` and `clamp()` functions (#426)
 - Fixed crash on bad value in TRBL declaration value (#412)
 
diff --git a/lib/clean/Declaration.js b/lib/clean/Declaration.js
index 28253a64..f3cac374 100644
--- a/lib/clean/Declaration.js
+++ b/lib/clean/Declaration.js
@@ -1,5 +1,14 @@
+var property = require('css-tree').property;
+
 module.exports = function cleanDeclartion(node, item, list) {
     if (node.value.children && node.value.children.isEmpty()) {
         list.remove(item);
+        return;
+    }
+
+    if (property(node.property).custom) {
+        if (/\S/.test(node.value.value)) {
+            node.value.value = node.value.value.trim();
+        }
     }
 };
diff --git a/test/fixture/compress/custom-property.min.css b/test/fixture/compress/custom-property.min.css
index 69a1f64d..494e815c 100644
--- a/test/fixture/compress/custom-property.min.css
+++ b/test/fixture/compress/custom-property.min.css
@@ -1 +1 @@
-:root{--mainColor: #fb4c42;--test-var: 5px;--foo: if(x > 5) this.width = 10}.test{color:var(--mainColor, blue);border:1px solid var(--test-var)}a::after{content:" (" var(--external-link) ")"}.example7{--main-color: #c06;--accent-background: linear-gradient(to top, var(--main-color), white)}.example8{--one: calc(var(--two) + 20px);--two: calc(var(--one) - 20px)}one{--foo: 10px}two{--bar: calc(var(--foo) + 10px)}three{--foo: calc(var(--bar) + 10px)}
+:root{--mainColor:#fb4c42;--test-var:5px;--foo:if(x > 5) this.width = 10}.test{color:var(--mainColor, blue);border:1px solid var(--test-var)}a::after{content:" (" var(--external-link) ")"}.example7{--main-color:#c06;--accent-background:linear-gradient(to top, var(--main-color), white)}.example8{--one:calc(var(--two) + 20px);--two:calc(var(--one) - 20px)}one{--foo:10px}two{--bar:calc(var(--foo) + 10px)}three{--foo:calc(var(--bar) + 10px)}