diff --git a/src/lib/custom-style.html b/src/lib/custom-style.html
index 0d750eac18..80c3e10925 100644
--- a/src/lib/custom-style.html
+++ b/src/lib/custom-style.html
@@ -134,6 +134,11 @@
       cases of ordering w.r.t the main document styles.
       */
       if (this.ownerDocument !== window.document && this.__appliedElement === this) {
+        // Allow users to add `type="custom"` to <style> tags to avoid deprecation warning
+        var type = this.getAttribute('type');
+        if (type == 'custom') {
+          this.removeAttribute('type');
+        }
         document.head.appendChild(this);
       }
       // needed becuase elements in imports do not get 'attached'
diff --git a/test/unit/custom-style-import.html b/test/unit/custom-style-import.html
index 3771b61212..c3baf2e8da 100644
--- a/test/unit/custom-style-import.html
+++ b/test/unit/custom-style-import.html
@@ -21,7 +21,7 @@
 <link rel="import" href="sub/style-import.html">
 
 <style is="custom-style" include="shared-style style-import
-    style-import2">
+    style-import2" type="custom" id="type-was-custom">
   :root {
 
     --import-mixin: {
diff --git a/test/unit/custom-style.html b/test/unit/custom-style.html
index 7b34a2f39a..132b6e1ed1 100644
--- a/test/unit/custom-style.html
+++ b/test/unit/custom-style.html
@@ -480,6 +480,11 @@
         assertComputed(m, '4px');
       });
 
+      test('imported custom-style style with type="custom" has type removed', function() {
+        const style = document.head.querySelector('style#type-was-custom');
+        assert.isFalse(style.hasAttribute('type'));
+      });
+
       test('dynamic custom-styles apply', function() {
         var dynamic = document.querySelector('.dynamic');
         assertComputed(dynamic, '0px');