diff --git a/spake2/Cargo.toml b/spake2/Cargo.toml
index e6097bf..953d2b8 100644
--- a/spake2/Cargo.toml
+++ b/spake2/Cargo.toml
@@ -30,11 +30,11 @@ curve25519-dalek = "1"
 rand = "0.6"
 sha2 = "0.8"
 hkdf = "0.7"
-num-bigint = "0.2"
 hex = "0.3"
 
 [dev-dependencies]
 bencher = "0.1"
+num-bigint = "0.2"
 
 [[bench]]
 name = "spake2"