diff --git a/components/style/stylesheets.rs b/components/style/stylesheets.rs
index 1689953ba8a..bc573eb4bfe 100644
--- a/components/style/stylesheets.rs
+++ b/components/style/stylesheets.rs
@@ -392,7 +392,7 @@ impl ToCss for ImportRule {
             try!(dest.write_str(" "));
             try!(media.to_css(dest));
         }
-        Ok(())
+        dest.write_str(";")
     }
 }
 
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index df134a0abb9..ca2f3db7589 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -6638,6 +6638,12 @@
             "url": "/_mozilla/css/float_relative_to_position.html"
           }
         ],
+        "css/import_serialization.html": [
+          {
+            "path": "css/import_serialization.html",
+            "url": "/_mozilla/css/import_serialization.html"
+          }
+        ],
         "css/matchMedia.html": [
           {
             "path": "css/matchMedia.html",
diff --git a/tests/wpt/mozilla/tests/css/import_serialization.html b/tests/wpt/mozilla/tests/css/import_serialization.html
new file mode 100644
index 00000000000..44c828db3cb
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/import_serialization.html
@@ -0,0 +1,16 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>CSS Test: @import rules are correctly serialized</title>
+<style id="test">
+  @import url("foo.css");
+  @import url("foo.css") print;
+</style>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function() {
+  var rules = document.styleSheets[0].cssRules;
+  assert_equals(rules[0].cssText, "@import url(\"foo.css\");");
+  assert_equals(rules[1].cssText, "@import url(\"foo.css\") print;");
+})
+</script>
