diff --git a/src/NRRD.jl b/src/NRRD.jl
index b5eabaa..978a455 100644
--- a/src/NRRD.jl
+++ b/src/NRRD.jl
@@ -58,7 +58,12 @@ const string2type = Dict(
 type2string(::Type{Float16}) = "float16"
 type2string(::Type{Float32}) = "float"
 type2string(::Type{Float64}) = "double"
-type2string(::Type{T}) where {T<:Integer} = lowercase(string(T.name.name))
+type2string(::Type{Bool})    = "uint8"   # bool is not supported
+function type2string(::Type{T}) where {T<:Integer}
+    str = lowercase(string(T.name.name))
+    haskey(string2type, str) && return str
+    error("integer type $T not supported")
+end
 type2string(::Type{Normed{T,f}}) where {T<:Unsigned,f} = type2string(T)
 type2string(::Type{T}) where {T} = type2string(eltype(T), T)
 type2string(::Type{T}, ::Type{T}) where {T} = error("type $T unrecognized")
diff --git a/test/runtests.jl b/test/runtests.jl
index 74bb97f..01e5f3a 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,6 +1,15 @@
 using FileIO, ImageCore, Unitful, AxisArrays, ImageAxes, ImageMetadata
 using Test, Base.CoreLogging
 
+struct UnsupportedInt16 <: Signed
+    val::Int16
+end
+Base.flipsign(x::UnsupportedInt16, y::UnsupportedInt16) = UnsupportedInt16(flipsign(x.val, y.val))
+Base.Unsigned(x::UnsupportedInt16) = Unsigned(x.val)
+Base.UInt16(x::UnsupportedInt16) = UInt16(x.val)
+Base.Int(x::UnsupportedInt16) = Int(x.val)
+Base.promote_rule(::Type{UnsupportedInt16}, ::Type{Int}) = Int
+
 include("unu-make.jl")
 
 @testset "NRRD" begin
@@ -102,6 +111,23 @@ include("unu-make.jl")
         end
     end
 
+    @testset "bool" begin
+        # Bool is not one of the supported eltypes in the `type` field of
+        # http://teem.sourceforge.net/nrrd/format.html.
+        # Make sure we don't do something wrong
+        fn = joinpath(writedir, "eltype_bool.nrrd")
+        img = rand(Bool, 5, 6)
+        save(fn, img)
+        imgr = load(fn)
+        @test imgr == img
+        # We don't insist on eltype(imgr) == Bool
+        img = UnsupportedInt16[1 2; 3 4]
+        @info "The following error is expected"
+        fn = joinpath(writedir, "eltype_unsupported.nrrd")
+        ex = try save(fn, img) catch e e end
+        @test ex.ex == ErrorException("integer type UnsupportedInt16 not supported")
+    end
+
     @testset "Mmapped" begin
         fn = joinpath(writedir, "volume.nrrd")
         save(fn, zeros(UInt8,500,500,500))