diff --git a/ssz/Cargo.toml b/ssz/Cargo.toml
index 0500ab3c5c..aa4dc5d72c 100644
--- a/ssz/Cargo.toml
+++ b/ssz/Cargo.toml
@@ -5,4 +5,4 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 
 [dependencies]
 bytes = "0.4.9"
-ethereum-types = ""
+ethereum-types = "0.4.0"