diff --git a/Project.toml b/Project.toml
index 8dc2bcf3..4a3379b5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -17,7 +17,7 @@ StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 Calculus = "0.2, 0.3, 0.4, 0.5"
 CommonSubexpressions = "0.3"
 DiffResults = "0.0.1, 0.0.2, 0.0.3, 0.0.4, 1.0.1"
-DiffRules = "0.0.4, 0.0.5, 0.0.6, 0.0.7, 0.0.8, 0.0.9, 0.0.10, 0.1, 1.0"
+DiffRules = "1.2.1"
 DiffTests = "0.0.1, 0.1"
 NaNMath = "0.2.2, 0.3"
 SpecialFunctions = "0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.10, 1.0"
diff --git a/src/dual.jl b/src/dual.jl
index 431bb3e5..62ce57be 100644
--- a/src/dual.jl
+++ b/src/dual.jl
@@ -378,8 +378,6 @@ Base.AbstractFloat(d::Dual{T,V,N}) where {T,V,N} = convert(Dual{T,promote_type(V
 # General Mathematical Operations #
 ###################################
 
-@inline Base.conj(d::Dual) = d
-
 for (M, f, arity) in DiffRules.diffrules()
     in((M, f), ((:Base, :^), (:NaNMath, :pow), (:Base, :/), (:Base, :+), (:Base, :-))) && continue
     if arity == 1