diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index 7e41fa80585..e66022d96ec 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -843,6 +843,10 @@ impl CalcLengthOrPercentage {
                 input.parse_nested_block(|i| CalcLengthOrPercentage::parse_sum(context, i, expected_unit))
                      .map(|result| CalcValueNode::Sum(Box::new(result)))
             },
+            (Token::Function(ref name), _) if name.eq_ignore_ascii_case("calc") => {
+                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_sum(context, i, expected_unit))
+                     .map(|result| CalcValueNode::Sum(Box::new(result)))
+            }
             _ => Err(())
         }
     }
diff --git a/tests/unit/style/parsing/length.rs b/tests/unit/style/parsing/length.rs
index 6b246484934..4263f2a08a1 100644
--- a/tests/unit/style/parsing/length.rs
+++ b/tests/unit/style/parsing/length.rs
@@ -16,6 +16,7 @@ use style_traits::ToCss;
 #[test]
 fn test_calc() {
     assert!(parse(Length::parse, "calc(1px+ 2px)").is_err());
+    assert!(parse(Length::parse, "calc(calc(1px) + calc(1px + 4px))").is_ok());
     assert!(parse(Length::parse, "calc( 1px + 2px )").is_ok());
     assert!(parse(Length::parse, "calc(1px + 2px )").is_ok());
     assert!(parse(Length::parse, "calc( 1px + 2px)").is_ok());
diff --git a/tests/wpt/metadata-css/css-values-3_dev/html/calc-in-calc.htm.ini b/tests/wpt/metadata-css/css-values-3_dev/html/calc-in-calc.htm.ini
deleted file mode 100644
index a6d81ffc78c..00000000000
--- a/tests/wpt/metadata-css/css-values-3_dev/html/calc-in-calc.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[calc-in-calc.htm]
-  type: reftest
-  expected: FAIL