--- a/layout/style/test/property_database.js
+++ b/layout/style/test/property_database.js
@@ -4203,18 +4203,19 @@ var gCSSProperties = {
   },
   "overflow": {
     domProp: "overflow",
     inherited: false,
     type: CSS_TYPE_SHORTHAND_AND_LONGHAND,
     prerequisites: { "display": "block", "contain": "none" },
     subproperties: [ "overflow-x", "overflow-y" ],
     initial_values: [ "visible" ],
-    other_values: [ "auto", "scroll", "hidden", "-moz-hidden-unscrollable", "-moz-scrollbars-none" ],
-    invalid_values: []
+    other_values: [ "auto", "scroll", "hidden", "-moz-hidden-unscrollable", "-moz-scrollbars-none",
+                    "auto auto", "auto scroll", "hidden scroll", "auto hidden" ],
+    invalid_values: [ "-moz-hidden-unscrollable -moz-hidden-unscrollable", "-moz-hidden-unscrollable -moz-scrollbars-none" ]
   },
   "overflow-x": {
     domProp: "overflowX",
     inherited: false,
     type: CSS_TYPE_LONGHAND,
     // No applies_to_placeholder because we have a !important rule in forms.css.
     prerequisites: { "display": "block", "overflow-y": "visible", "contain": "none" },
     initial_values: [ "visible" ],

--- a/servo/components/style/properties/shorthand/box.mako.rs
+++ b/servo/components/style/properties/shorthand/box.mako.rs
@@ -1,16 +1,19 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 <%namespace name="helpers" file="/helpers.mako.rs" />
 
-<%helpers:shorthand name="overflow" sub_properties="overflow-x overflow-y"
-                    spec="https://drafts.csswg.org/css-overflow/#propdef-overflow">
+<%helpers:shorthand
+    name="overflow"
+    sub_properties="overflow-x overflow-y"
+    spec="https://drafts.csswg.org/css-overflow/#propdef-overflow"
+>
     use properties::longhands::overflow_x::parse as parse_overflow;
     % if product == "gecko":
         use properties::longhands::overflow_x::SpecifiedValue;
     % endif
 
     pub fn parse_value<'i, 't>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
@@ -37,30 +40,33 @@
                         })
                     }
                 }
             });
             if moz_kw_found.is_ok() {
                 return moz_kw_found
             }
         % endif
-        let overflow = parse_overflow(context, input)?;
+        let overflow_x = parse_overflow(context, input)?;
+        let overflow_y =
+            input.try(|i| parse_overflow(context, i)).unwrap_or(overflow_x);
         Ok(expanded! {
-            overflow_x: overflow,
-            overflow_y: overflow,
+            overflow_x: overflow_x,
+            overflow_y: overflow_y,
         })
     }
 
     impl<'a> ToCss for LonghandsToSerialize<'a>  {
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
-            if self.overflow_x == self.overflow_y {
-                self.overflow_x.to_css(dest)
-            } else {
-                Ok(())
+            self.overflow_x.to_css(dest)?;
+            if self.overflow_x != self.overflow_y {
+                dest.write_char(' ')?;
+                self.overflow_y.to_css(dest)?;
             }
+            Ok(())
         }
     }
 </%helpers:shorthand>
 
 <%helpers:shorthand
     name="overflow-clip-box"
     sub_properties="overflow-clip-box-block overflow-clip-box-inline"
     enabled_in="ua"

--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -313618,16 +313618,22 @@
     ]
    ],
    "css/css-multicol/multicol-gap-percentage-001.html": [
     [
      "/css/css-multicol/multicol-gap-percentage-001.html",
      {}
     ]
    ],
+   "css/css-overflow/overflow-shorthand-001.html": [
+    [
+     "/css/css-overflow/overflow-shorthand-001.html",
+     {}
+    ]
+   ],
    "css/css-position/position-sticky-bottom.html": [
     [
      "/css/css-position/position-sticky-bottom.html",
      {}
     ]
    ],
    "css/css-position/position-sticky-get-bounding-client-rect.html": [
     [
@@ -503525,16 +503531,20 @@
   "css/css-namespaces/syntax-016.xml": [
    "0cba1aed016d08e4706bffb8a4f4169c9cfd2108",
    "visual"
   ],
   "css/css-overflow/input-scrollable-region-001.html": [
    "f51bc673da28b0471018cdf945b4449ab00ce717",
    "reftest"
   ],
+  "css/css-overflow/overflow-shorthand-001.html": [
+   "6409ee499d3e853d8f4933f1b532e12ed9ab406b",
+   "testharness"
+  ],
   "css/css-overflow/reference/input-scrollable-region-001-ref.html": [
    "31e24bb1a2cb6f42703cc05e055fcb345c770a22",
    "support"
   ],
   "css/css-page/OWNERS": [
    "d4ee6029cc9c064e0e8b2c76becf3b59c4f7b62b",
    "support"
   ],

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/tests/css/css-overflow/overflow-shorthand-001.html
@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Overflow Test: Overflow longhand accepts two values</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<link rel="author" title="Emilio Cobos Álvarez <emilio@crisal.io>">
+<link rel="help" href="https://drafts.csswg.org/css-overflow/#propdef-overflow">
+<div id="test-div"></div>
+<script>
+let div = document.getElementById("test-div");
+function testOverflowShorthand(x, y) {
+  test(function() {
+    div.style.overflowX = x;
+    div.style.overflowY = y;
+
+    let expectedX = getComputedStyle(div).overflowX;
+    let expectedY = getComputedStyle(div).overflowY;
+    let expectedSerialization = x == y ? x : `${x} ${y}`;
+
+    assert_equals(div.style.overflow, expectedSerialization);
+
+    div.style.overflowX = "";
+    div.style.overflowY = "";
+    assert_equals(div.style.overflow, "");
+
+    div.style.overflow = `${x} ${y}`;
+    assert_equals(div.style.overflow, expectedSerialization);
+    assert_equals(getComputedStyle(div).overflowX, expectedX);
+    assert_equals(getComputedStyle(div).overflowY, expectedY);
+  }, `overflow: ${x} ${y} works`);
+}
+
+let OVERFLOW_VALUES = [ "auto", "hidden", "scroll" ];
+for (let x of OVERFLOW_VALUES)
+  for (let y of OVERFLOW_VALUES)
+    testOverflowShorthand(x, y);
+</script>