diff --git a/src/dual.jl b/src/dual.jl
index 22129b68..8f557860 100644
--- a/src/dual.jl
+++ b/src/dual.jl
@@ -98,7 +98,7 @@ macro define_binary_dual_op(f, xy_body, x_body, y_body)
         @inline $(f)(x::Dual{Txy}, y::Dual{Txy}) where {Txy} = $xy_body
         @inline $(f)(x::Dual{Tx}, y::Dual{Ty}) where {Tx,Ty} = Ty ≺ Tx ? $x_body : $y_body
     end
-    for R in REAL_TYPES
+    for R in AMBIGUOUS_TYPES
         expr = quote
             @inline $(f)(x::Dual{Tx}, y::$R) where {Tx} = $x_body
             @inline $(f)(x::$R, y::Dual{Ty}) where {Ty} = $y_body
@@ -124,7 +124,7 @@ macro define_ternary_dual_op(f, xyz_body, xy_body, xz_body, yz_body, x_body, y_b
             end
         end
     end
-    for R in REAL_TYPES
+    for R in AMBIGUOUS_TYPES
         expr = quote
             @inline $(f)(x::Dual{Txy}, y::Dual{Txy}, z::$R) where {Txy} = $xy_body
             @inline $(f)(x::Dual{Tx}, y::Dual{Ty}, z::$R)  where {Tx, Ty} = Ty ≺ Tx ? $x_body : $y_body
@@ -134,7 +134,7 @@ macro define_ternary_dual_op(f, xyz_body, xy_body, xz_body, yz_body, x_body, y_b
             @inline $(f)(x::$R, y::Dual{Ty}, z::Dual{Tz}) where {Ty,Tz} = Tz ≺ Ty ? $y_body : $z_body
         end
         append!(defs.args, expr.args)
-        for Q in REAL_TYPES
+        for Q in AMBIGUOUS_TYPES
             Q === R && continue
             expr = quote
                 @inline $(f)(x::Dual{Tx}, y::$R, z::$Q) where {Tx} = $x_body
diff --git a/src/prelude.jl b/src/prelude.jl
index d3748fe4..4e3fa9b5 100644
--- a/src/prelude.jl
+++ b/src/prelude.jl
@@ -1,6 +1,6 @@
 const NANSAFE_MODE_ENABLED = false
 
-const REAL_TYPES = (AbstractFloat, Irrational, Integer, Rational, Real)
+const AMBIGUOUS_TYPES = (AbstractFloat, Irrational, Integer, Rational, Real, RoundingMode)
 
 const UNARY_PREDICATES = Symbol[:isinf, :isnan, :isfinite, :iseven, :isodd, :isreal, :isinteger]
 
diff --git a/test/DualTest.jl b/test/DualTest.jl
index d2686a1d..4d6f1a8c 100644
--- a/test/DualTest.jl
+++ b/test/DualTest.jl
@@ -19,10 +19,9 @@ samerng() = MersenneTwister(1)
 intrand(V) = V == Int ? rand(2:10) : rand(V)
 
 dual_isapprox(a, b) = isapprox(a, b)
-dual_isapprox(a::Dual{T,T1,T2}, b::Dual{T,T3,T4}) where {T,T1,T2,T3,T4} =
-            isapprox(value(a), value(b)) && isapprox(partials(a), partials(b))
-dual_isapprox(a::Dual{T,T1,T2}, b::Dual{T3,T4,T5}) where {T,T1,T2,T3,T4,T5} =
-            error("Tags don't match")
+dual_isapprox(a::Dual{T,T1,T2}, b::Dual{T,T3,T4}) where {T,T1,T2,T3,T4} = isapprox(value(a), value(b)) && isapprox(partials(a), partials(b))
+dual_isapprox(a::Dual{T,T1,T2}, b::Dual{T3,T4,T5}) where {T,T1,T2,T3,T4,T5} = error("Tags don't match")
+
 ForwardDiff.:≺(::Type{TestTag()}, ::Int) = true
 ForwardDiff.:≺(::Int, ::Type{TestTag()}) = false
 
@@ -394,7 +393,7 @@ for N in (0,3), M in (0,4), V in (Int, Float32)
 
     if V != Int
         for (M, f, arity) in DiffRules.diffrules()
-            in(f, (:hankelh1, :hankelh1x, :hankelh2, :hankelh2x, :/)) && continue
+            in(f, (:hankelh1, :hankelh1x, :hankelh2, :hankelh2x, :/, :rem2pi)) && continue
             println("       ...auto-testing $(M).$(f) with $arity arguments")
             if arity == 1
                 deriv = DiffRules.diffrule(M, f, :x)