diff --git a/src/alphabet.jl b/src/alphabet.jl
index 06b7ffa6..716a92ff 100644
--- a/src/alphabet.jl
+++ b/src/alphabet.jl
@@ -94,7 +94,15 @@ end
 EncodeError(::A, val::T) where {A,T} = EncodeError{A,T}(val)
 
 function Base.showerror(io::IO, err::EncodeError{A}) where {A}
-    print(io, "cannot encode ", err.val, " in ", A)
+    val = err.val
+    char_repr = if val isa Integer && val < 0x80
+        repr(val) * " (Char '" * Char(val) * "')"
+    elseif val isa Union{AbstractString, AbstractChar}
+        repr(val)
+    else
+        string(err.val)
+    end
+    print(io, "cannot encode " * char_repr * " in ", A)
 end
 
 """
diff --git a/src/biosequence/biosequence.jl b/src/biosequence/biosequence.jl
index f71ea95f..a5c3c2d7 100644
--- a/src/biosequence/biosequence.jl
+++ b/src/biosequence/biosequence.jl
@@ -60,7 +60,7 @@ function has_interface(
         isempty(syms) && error("Vector syms must not be empty")
         first(syms) isa eltype(T) || error("Vector is of wrong element type")
         seq = T((i for i in syms))
-        length(seq) > 0 || return false
+        length(seq) == length(syms) || return false
         eachindex(seq) === Base.OneTo(length(seq)) || return false
         E = encoded_data_eltype(T)
         e = extract_encoded_element(seq, 1)
@@ -87,13 +87,14 @@ Base.nextind(::BioSequence, i::Integer) = Int(i) + 1
 Base.prevind(::BioSequence, i::Integer) = Int(i) - 1
 Base.size(x::BioSequence) = (length(x),)
 Base.eltype(::Type{<:BioSequence{A}}) where {A <: Alphabet} = eltype(A)
-Base.eltype(x::BioSequence) = eltype(typeof(x))
 Alphabet(::Type{<:BioSequence{A}}) where {A <: Alphabet} = A()
 Alphabet(x::BioSequence) = Alphabet(typeof(x))
 Base.isempty(x::BioSequence) = iszero(length(x))
 Base.empty(::Type{T}) where {T <: BioSequence} = T(eltype(T)[])
 Base.empty(x::BioSequence) = empty(typeof(x))
 BitsPerSymbol(x::BioSequence) = BitsPerSymbol(Alphabet(typeof(x)))
+bits_per_symbol(::Type{T}) where {T <: BioSequence} = bits_per_symbol(Alphabet(T))
+bits_per_symbol(x::BioSequence) = bits_per_symbol(typeof(x))
 Base.hash(s::BioSequence, x::UInt) = foldl((a, b) -> hash(b, a), s, init=x)
 
 function Base.similar(seq::BioSequence, len::Integer=length(seq))
diff --git a/src/bit-manipulation/bit-manipulation.jl b/src/bit-manipulation/bit-manipulation.jl
index cb447287..8623c5a8 100644
--- a/src/bit-manipulation/bit-manipulation.jl
+++ b/src/bit-manipulation/bit-manipulation.jl
@@ -2,19 +2,37 @@
 include("bitindex.jl")
 include("bitpar-compiler.jl")
 
-@inline function reversebits(x::T, ::BitsPerSymbol{2}) where T <: Base.BitUnsigned
+const BitUnsigned = Union{UInt8, UInt16, UInt32, UInt64, UInt128}
+
+@inline function reversebits(x::T, ::BitsPerSymbol{2}) where T <: BitUnsigned
      mask = 0x33333333333333333333333333333333 % T
      x = ((x >> 2) & mask) | ((x & mask) << 2)
      return reversebits(x, BitsPerSymbol{4}())
 end
 
-@inline function reversebits(x::T, ::BitsPerSymbol{4}) where T <: Base.BitUnsigned
+@inline function reversebits(x::T, ::BitsPerSymbol{4}) where T <: BitUnsigned
      mask = 0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F % T
      x = ((x >> 4) & mask) | ((x & mask) << 4)
-     return bswap(x)
+     return reversebits(x, BitsPerSymbol{8}())
+end
+
+@inline reversebits(x::T, ::BitsPerSymbol{8}) where T <: BitUnsigned = bswap(x)
+
+@inline reversebits(x::UInt16, ::BitsPerSymbol{16}) = x
+@inline function reversebits(x::T, ::BitsPerSymbol{16}) where T <: Union{UInt32, UInt64}
+    mask = 0x0000FFFF0000FFFF0000FFFF0000FFFF % T
+    x = ((x >> 16) & mask) | ((x & mask) << 16)
+    reversebits(x, BitsPerSymbol{32}())
+end
+
+@inline reversebits(x::UInt32, ::BitsPerSymbol{32}) = x
+@inline function reversebits(x::T, ::BitsPerSymbol{32}) where T <: Union{UInt64}
+    mask = 0x00000000FFFFFFF00000000FFFFFFFF % T
+    x = ((x >> 32) & mask) | ((x & mask) << 32)
+    reversebits(x, BitsPerSymbol{64}())
 end
 
-reversebits(x::T, ::BitsPerSymbol{8}) where T <: Base.BitUnsigned = bswap(x)
+@inline reversebits(x::UInt64, ::BitsPerSymbol{64}) = x
 
 @inline function complement_bitpar(x::Unsigned, ::T) where {T<:NucleicAcidAlphabet{2}}
     return ~x