diff --git a/Cargo.lock b/Cargo.lock
index 34643bd0e8b..818493ea05f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1693,6 +1693,7 @@ dependencies = [
  "euclid 0.16.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashglobe 0.1.0",
  "mozjs 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "selectors 0.19.0",
  "servo_arc 0.0.1",
  "smallbitvec 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2717,8 +2718,6 @@ dependencies = [
  "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "malloc_size_of 0.0.1",
- "malloc_size_of_derive 0.0.1",
  "matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/components/malloc_size_of/Cargo.toml b/components/malloc_size_of/Cargo.toml
index a5c3acfb861..9b24d6dade8 100644
--- a/components/malloc_size_of/Cargo.toml
+++ b/components/malloc_size_of/Cargo.toml
@@ -17,6 +17,7 @@ cssparser = "0.23.0"
 euclid = "0.16"
 hashglobe = { path = "../hashglobe" }
 mozjs = { version = "0.1.8", features = ["promises"], optional = true }
+selectors = { path = "../selectors" }
 servo_arc = { path = "../servo_arc" }
 smallbitvec = "1.0.3"
 smallvec = "0.6"
diff --git a/components/malloc_size_of/lib.rs b/components/malloc_size_of/lib.rs
index b366de512f0..2ec16f380de 100644
--- a/components/malloc_size_of/lib.rs
+++ b/components/malloc_size_of/lib.rs
@@ -49,6 +49,7 @@ extern crate euclid;
 extern crate hashglobe;
 #[cfg(feature = "servo")]
 extern crate mozjs as js;
+extern crate selectors;
 extern crate servo_arc;
 extern crate smallbitvec;
 extern crate smallvec;
@@ -640,6 +641,13 @@ impl<T: MallocSizeOf, U> MallocSizeOf for euclid::TypedVector2D<T, U> {
     }
 }
 
+impl MallocSizeOf for selectors::parser::AncestorHashes {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        let selectors::parser::AncestorHashes { ref packed_hashes } = *self;
+        packed_hashes.size_of(ops)
+    }
+}
+
 #[cfg(feature = "servo")]
 impl<Static: string_cache::StaticAtomSet> MallocSizeOf for string_cache::Atom<Static> {
     fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
diff --git a/components/selectors/Cargo.toml b/components/selectors/Cargo.toml
index 86466213adc..0dfca53e32f 100644
--- a/components/selectors/Cargo.toml
+++ b/components/selectors/Cargo.toml
@@ -26,8 +26,6 @@ matches = "0.1"
 cssparser = "0.23.0"
 log = "0.3"
 fnv = "1.0"
-malloc_size_of = { path = "../malloc_size_of" }
-malloc_size_of_derive = { path = "../malloc_size_of_derive" }
 phf = "0.7.18"
 precomputed-hash = "0.1"
 servo_arc = { path = "../servo_arc" }
diff --git a/components/selectors/lib.rs b/components/selectors/lib.rs
index c8e7ce175d5..a0f929ecfbb 100644
--- a/components/selectors/lib.rs
+++ b/components/selectors/lib.rs
@@ -10,8 +10,6 @@
 #[macro_use] extern crate log;
 #[macro_use] extern crate matches;
 extern crate fnv;
-extern crate malloc_size_of;
-#[macro_use] extern crate malloc_size_of_derive;
 extern crate phf;
 extern crate precomputed_hash;
 #[cfg(test)] #[macro_use] extern crate size_of_test;
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 99b73353abf..e39ba36bd4e 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -266,7 +266,7 @@ where
 /// off the upper bits) at the expense of making the fourth somewhat more
 /// complicated to assemble, because we often bail out before checking all the
 /// hashes.
-#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct AncestorHashes {
     pub packed_hashes: [u32; 3],
 }