diff --git a/components/style/properties/longhand/box.mako.rs b/components/style/properties/longhand/box.mako.rs
index d6a7f015e50..3a02b6c656d 100644
--- a/components/style/properties/longhand/box.mako.rs
+++ b/components/style/properties/longhand/box.mako.rs
@@ -507,16 +507,17 @@ ${helpers.single_keyword("overflow-x", "visible hidden scroll auto",
                     Ok(TransitionTimingFunction::CubicBezier(p1, p2))
                 },
                 "steps" => {
-                    let (mut step_count, mut start_end) = (0, computed_value::StartEnd::Start);
+                    let (mut step_count, mut start_end) = (0, computed_value::StartEnd::End);
                     try!(input.parse_nested_block(|input| {
                         step_count = try!(specified::parse_integer(input));
-                        try!(input.expect_comma());
-                        start_end = try!(match_ignore_ascii_case! {
-                            try!(input.expect_ident()),
-                            "start" => Ok(computed_value::StartEnd::Start),
-                            "end" => Ok(computed_value::StartEnd::End),
-                            _ => Err(())
-                        });
+                        if input.try(|input| input.expect_comma()).is_ok() {
+                            start_end = try!(match_ignore_ascii_case! {
+                                try!(input.expect_ident()),
+                                "start" => Ok(computed_value::StartEnd::Start),
+                                "end" => Ok(computed_value::StartEnd::End),
+                                _ => Err(())
+                            });
+                        }
                         Ok(())
                     }));
                     Ok(TransitionTimingFunction::Steps(step_count as u32, start_end))
diff --git a/tests/wpt/metadata-css/css-transitions-1_dev/html/transition-timing-function-001.htm.ini b/tests/wpt/metadata-css/css-transitions-1_dev/html/transition-timing-function-001.htm.ini
index 1d3aaf317a8..e5ec8603b1e 100644
--- a/tests/wpt/metadata-css/css-transitions-1_dev/html/transition-timing-function-001.htm.ini
+++ b/tests/wpt/metadata-css/css-transitions-1_dev/html/transition-timing-function-001.htm.ini
@@ -1,8 +1,5 @@
 [transition-timing-function-001.htm]
   type: testharness
-  [parse 'steps(3)']
-    expected: FAIL
-
   [parse 'cubic-bezier(-0.1, -0.2, -0.3, -0.4)']
     expected: FAIL