diff --git a/util/hashdb/Cargo.toml b/util/hashdb/Cargo.toml
index 6ac3967ca50..962f0e7f694 100644
--- a/util/hashdb/Cargo.toml
+++ b/util/hashdb/Cargo.toml
@@ -7,7 +7,7 @@ license = "GPL-3.0"
 
 [dependencies]
 elastic-array = "0.10"
-ethereum-types = "0.3"
 heapsize = "0.4"
-tiny-keccak = "1.4.2"
-rlp = "*"
\ No newline at end of file
+# TODO: Used by the `KeccakHasher` impl which I think should move to own crate?
+ethereum-types = "0.3"
+tiny-keccak = "1.4.2"
\ No newline at end of file
diff --git a/util/hashdb/src/lib.rs b/util/hashdb/src/lib.rs
index 01461689737..0a9a9fc588f 100644
--- a/util/hashdb/src/lib.rs
+++ b/util/hashdb/src/lib.rs
@@ -19,7 +19,6 @@ extern crate elastic_array;
 extern crate ethereum_types;
 extern crate heapsize;
 extern crate tiny_keccak;
-extern crate rlp;
 
 use elastic_array::ElasticArray128;
 use ethereum_types::H256;
@@ -29,7 +28,7 @@ use std::{fmt::Debug, hash::Hash};
 use tiny_keccak::Keccak;
 
 pub trait Hasher: Sync + Send {
-	type Out: AsRef<[u8]> + Debug + PartialEq + Eq + Clone + Copy + Hash + Send + Sync /* REVIEW: how do I get around this? --> */ + HeapSizeOf /* …and this? -> */ + rlp::Decodable;
+	type Out: AsRef<[u8]> + Debug + PartialEq + Eq + Clone + Copy + Hash + Send + Sync /* REVIEW: how do I get around this? --> */ + HeapSizeOf;
 	const HASHED_NULL_RLP: Self::Out;
 	fn hash(x: &[u8]) -> Self::Out;
 }