diff --git a/packages/minifier-css/minifier.js b/packages/minifier-css/minifier.js
index bd88ede21d..0994ee6fc8 100644
--- a/packages/minifier-css/minifier.js
+++ b/packages/minifier-css/minifier.js
@@ -136,8 +136,9 @@ var rewriteRules = function (rules, mergedCssPath) {
 
 
         // We don't rewrite URLs starting with a protocol definition such as
-        // http, https, or data.
-        if (resource.protocol !== null) {
+        // http, https, or data, or those with network-path references
+        // i.e. //img.domain.com/cat.gif
+        if (resource.protocol !== null || resource.href.startsWith('//')) {
           continue;
         }