diff --git a/Project.toml b/Project.toml
index 6e3d788..ae94c70 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "PermutationGroups"
 uuid = "8bc5a954-2dfc-11e9-10e6-cd969bffa420"
 authors = ["Marek Kaluba <kalmar@amu.edu.pl>", "tweisser <tillmann.weisser@web.de>"]
-version = "0.4.2"
+version = "0.4.3"
 
 [deps]
 GroupsCore = "d5909c97-4eac-4ecc-a3dc-fdd0858a4120"
diff --git a/src/io.jl b/src/io.jl
index 7c9a963..a93e823 100644
--- a/src/io.jl
+++ b/src/io.jl
@@ -1,9 +1,3 @@
-function Base.show(io::IO, ::Type{<:PermGroup{I}}) where {I}
-    return print(io, PermGroup, "{$I, …}")
-end
-# function Base.show(io::IO, ::Type{<:Permutation{I, G}}) where {I, G}
-#     return print(io, Permutation, "{$I, …}")
-# end
 function Base.show(io::IO, G::PermGroup)
     print(io, "PermGroup( ")
     join(io, gens(G), ", ")
@@ -25,5 +19,3 @@ function Base.show(io::IO, ::MIME"text/plain", G::PermGroup)
     )
     return Base.print_array(io, gens(G))
 end
-
-# Base.show(io::IO, g::Permutation) = show(io, Perm.perm(g))
diff --git a/src/perm_group.jl b/src/perm_group.jl
index d004962..9f650f5 100644
--- a/src/perm_group.jl
+++ b/src/perm_group.jl
@@ -16,6 +16,7 @@ and stabilizer chain are computed (and cached) _when needed_.
             T::Type{<:AbstractTransversal},
             gens::AbstractVector{<:AbstractPermutation},
         )
+            @assert !isempty(gens) "groups need to have at least one generator"
             gens_raw = [Perms.perm(s) for s in gens]
             return new{eltype(gens_raw),T(eltype(gens_raw))}(gens_raw)
         end
@@ -31,6 +32,7 @@ else
             T::Type{<:AbstractTransversal},
             gens::AbstractVector{<:AbstractPermutation},
         )
+            @assert !isempty(gens) "groups need to have at least one generator"
             gens_raw = [Perms.perm(s) for s in gens]
             return new{eltype(gens_raw),T(eltype(gens_raw))}(gens_raw)
         end
diff --git a/test/perm_groups.jl b/test/perm_groups.jl
index ec53943..ad99ece 100644
--- a/test/perm_groups.jl
+++ b/test/perm_groups.jl
@@ -8,6 +8,8 @@
     @test order(Int, G) isa Int
     @test isdefined(G, :stabchain) == true
 
+    @test_throws AssertionError PermGroup()
+
     G = PermGroup(perm"(1,2)", perm"(1,2,3,4)")
     @test StabilizerChain(G) isa StabilizerChain
     sc = StabilizerChain(G)
@@ -40,8 +42,6 @@
     @test sprint(show, G) == "PermGroup( (1,2), (1,2,3,4) )"
     @test sprint(show, MIME"text/plain"(), G) ==
           "Permutation group on 2 generators generated by\n (1,2)\n (1,2,3,4)"
-    @test sprint(show, [G]) ==
-          "PermGroup{Perm{UInt16}, …}[PermGroup( (1,2), (1,2,3,4) )]"
 
     m = match(r"order (\d+)", sprint(show, MIME"text/plain"(), G))
     @test m === nothing