diff --git a/Project.toml b/Project.toml
index 27f3f9f..c010e17 100644
--- a/Project.toml
+++ b/Project.toml
@@ -4,11 +4,13 @@ authors = ["Fengyang Wang <fengyang.wang.0@gmail.com>", "Curtis Vogt <curtis.vog
 version = "0.4.0"
 
 [compat]
+Aqua = "0.5.5"
 julia = "1.6"
 
 [extras]
+Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Printf", "Test"]
+test = ["Printf", "Test", "Aqua"]
diff --git a/src/FixedPointDecimals.jl b/src/FixedPointDecimals.jl
index b7f5dc8..e0b7b21 100644
--- a/src/FixedPointDecimals.jl
+++ b/src/FixedPointDecimals.jl
@@ -123,6 +123,12 @@ function Base.widemul(x::FD{T, f}, y::Integer) where {T, f}
     reinterpret(FD{typeof(i), f}, i)
 end
 Base.widemul(x::Integer, y::FD) = widemul(y, x)
+# needed to avoid ambiguities
+function Base.widemul(x::FD{T, f}, y::Bool) where {T, f}
+    i = widemul(x.i, y)
+    reinterpret(FD{typeof(i), f}, i)
+end
+Base.widemul(x::Bool, y::FD) = widemul(y, x)
 
 """
     _round_to_even(quotient, remainder, divisor)
@@ -239,13 +245,20 @@ for fn in [:trunc, :floor, :ceil]
     @eval (Base.$fn(::Type{TI}, x::FD)::TI) where {TI <: Integer} = $fn(x)
 
     # round/trunc/ceil/flooring to FD; generic
-    @eval function Base.$fn(::Type{FD{T, f}}, x::Real) where {T, f}
+    @eval function $(Symbol(:_, fn))(::Type{FD{T, f}}, x::Real) where {T, f}
         powt = coefficient(FD{T, f})
         # Use machine Float64 if possible, but fall back to BigFloat if we need
         # more precision. 4f bits suffices.
         val = _apply_exact_float($(Symbol(fn, "mul")), T, x, powt)
         reinterpret(FD{T, f}, val)
     end
+    @eval function Base.$fn(::Type{FD{T, f}}, x::Real) where {T, f}
+        $(Symbol(:_, fn))(FD{T, f}, x)
+    end
+    # needed to avoid ambiguities
+    @eval function Base.$fn(::Type{FD{T, f}}, x::Rational) where {T, f}
+        $(Symbol(:_, fn))(FD{T, f}, x)
+    end
 end
 function Base.round(::Type{TI}, x::FD, ::RoundingMode{:Nearest}=RoundNearest) where {TI <: Integer}
     convert(TI, round(x))::TI
@@ -254,8 +267,17 @@ function Base.round(::Type{FD{T, f}}, x::Real, ::RoundingMode{:Nearest}=RoundNea
     reinterpret(FD{T, f}, round(T, x * coefficient(FD{T, f})))
 end
 
-# needed to avoid ambiguity
-function Base.round(::Type{FD{T, f}}, x::Rational, ::RoundingMode{:Nearest}=RoundNearest) where {T, f}
+# needed to avoid ambiguities
+@static if Base.VERSION >= v"1.6"
+    function Base.round(::Type{FD{T, f}}, x::Rational{Tr}, ::RoundingMode{:Nearest}=RoundNearest) where {T, Tr, f}
+        reinterpret(FD{T, f}, round(T, x * coefficient(FD{T, f})))
+    end
+else  # COV_EXCL_START
+    function Base.round(::Type{FD{T, f}}, x::Rational, ::RoundingMode{:Nearest}=RoundNearest) where {T, f}
+        reinterpret(FD{T, f}, round(T, x * coefficient(FD{T, f})))
+    end
+end  # COV_EXCL_STOP
+function Base.round(::Type{FD{T, f}}, x::Rational{Bool}, ::RoundingMode{:Nearest}=RoundNearest) where {T, f}
     reinterpret(FD{T, f}, round(T, x * coefficient(FD{T, f})))
 end
 
@@ -325,6 +347,8 @@ function Base.convert(::Type{TR}, x::FD{T, f}) where {TR <: Rational, T, f}
 end
 
 (::Type{T})(x::FD) where {T<:Union{AbstractFloat,Integer,Rational}} = convert(T, x)
+# needed to avoid ambiguities
+Bool(x::FD) = x == 0 ? false : (x == 1 ? true : throw(InexactError(:Bool, Bool, x)))
 
 Base.promote_rule(::Type{FD{T, f}}, ::Type{<:Integer}) where {T, f} = FD{T, f}
 Base.promote_rule(::Type{<:FD}, ::Type{TF}) where {TF <: AbstractFloat} = TF
diff --git a/test/runtests.jl b/test/runtests.jl
index 230a021..a77ad83 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1045,4 +1045,24 @@ end
     end
 end
 
+@testset "method ambiguities" begin
+    fd1 = FD{Int8, 1}(0.1)
+    fd2 = FD{Int, 1}(1.0)
+
+    @test widemul(fd1, false) == widemul(false, fd1) == FD{Int8, 1}(0.0)
+    @test ceil(FD{Int, 1}, 99 // 100) == fd2
+    @test round(FD{Int, 1}, true // true) == fd2
+    @test invoke(round, Tuple{Type{FD{Int, 1}}, Rational}, FD{Int, 1}, 99 // 100) == fd2
+
+    @test Bool(fd2)
+    @test_throws InexactError Bool(fd1)
+end
+
+@static if Base.VERSION >= v"1.6"
+    using Aqua
+    @testset "Aqua.jl" begin
+        Aqua.test_all(FixedPointDecimals)
+    end
+end
+
 end  # global testset