diff --git a/packages/postcss-convert-values/src/__tests__/index.js b/packages/postcss-convert-values/src/__tests__/index.js
index b767ceff4..425661216 100644
--- a/packages/postcss-convert-values/src/__tests__/index.js
+++ b/packages/postcss-convert-values/src/__tests__/index.js
@@ -67,6 +67,11 @@ test(
   processCSS('h1{width:100.00%}', 'h1{width:100%}')
 );
 
+test(
+  'should preserve opacities defined as percentages',
+  passthroughCSS('h1{opacity:100%}')
+);
+
 test('should not mangle flex basis', passthroughCSS('h1{flex-basis:0%}'));
 
 test('should not mangle flex basis (2)', passthroughCSS('h1{FLEX-BASIC:0%}'));
diff --git a/packages/postcss-convert-values/src/index.js b/packages/postcss-convert-values/src/index.js
index a8b0f9ce2..7da38f84b 100644
--- a/packages/postcss-convert-values/src/index.js
+++ b/packages/postcss-convert-values/src/index.js
@@ -53,7 +53,7 @@ function clampOpacity(node) {
   }
   let num = Number(pair.number);
   if (num > 1) {
-    node.value = 1 + pair.unit;
+    node.value = pair.unit === '%' ? num + pair.unit : 1 + pair.unit;
   } else if (num < 0) {
     node.value = 0 + pair.unit;
   }