diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e0e55c6..f562aa0f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ master
 * Correctly show file names of GZIP'ed assets. #1364
 * Build file output is not parallel-ized! Use `middleman build --no-parallel` to disable.
 * Make template file extensions that get layouts by default configurable via `config[:extensions_with_layout]`
+* Remove `=` from inline url matcher. This means paths in HTML attributes MUST be quoted. Fixes #1780
 
 # 4.0.0
 
diff --git a/middleman-core/features/asset_host.feature b/middleman-core/features/asset_host.feature
index 4cd733aa..646f1154 100644
--- a/middleman-core/features/asset_host.feature
+++ b/middleman-core/features/asset_host.feature
@@ -17,6 +17,8 @@ Feature: Alternate between multiple asset hosts
     When I go to "/stylesheets/asset_host.css"
     Then I should see content matching %r{http://assets1.example.com/}
     Then I should not see content matching %r{http://assets1.example.com//}
+    When I go to "/javascripts/asset_host.js"
+    Then I should not see content matching %r{http://assets1.example.com/}
 
   Scenario: Set proc host with inline-option
     Given a fixture app "asset-host-app"
diff --git a/middleman-core/lib/middleman-core/util.rb b/middleman-core/lib/middleman-core/util.rb
index f492a54d..cfbcb9ee 100644
--- a/middleman-core/lib/middleman-core/util.rb
+++ b/middleman-core/lib/middleman-core/util.rb
@@ -341,7 +341,7 @@ module Middleman
 
     Contract String, String, ArrayOf[String], Proc => String
     def rewrite_paths(body, _path, exts, &_block)
-      matcher = /([=\'\"\(,]\s*)([^\s\'\"\)>]+(#{Regexp.union(exts)}))/
+      matcher = /([\'\"\(,]\s*)([^\s\'\"\)>]+(#{Regexp.union(exts)}))/
 
       url_fn_prefix = 'url('