diff --git a/base/char.jl b/base/char.jl
index 52aa1492e2f862..e28217dc8c10ad 100644
--- a/base/char.jl
+++ b/base/char.jl
@@ -32,6 +32,8 @@ in(x::Char, y::Char) = x == y
 ==(x::Char, y::Char) = UInt32(x) == UInt32(y)
 isless(x::Char, y::Char) = UInt32(x) < UInt32(y)
 
+transpose(c::Char) = c
+
 const hashchar_seed = 0xd4d64234
 hash(x::Char, h::UInt) = hash_uint64(((UInt64(x)+hashchar_seed)<<32) $ UInt64(h))
 
diff --git a/base/operators.jl b/base/operators.jl
index 6570a14e3e6127..5b8ec3d5490718 100644
--- a/base/operators.jl
+++ b/base/operators.jl
@@ -293,7 +293,7 @@ fldmod1{T<:Real}(x::T, y::T) = (fld1(x,y), mod1(x,y))
 fldmod1{T<:Integer}(x::T, y::T) = (fld1(x,y), mod1(x,y))
 
 # transpose
-transpose(x) = x
+transpose(x) = error("transpose not implemented for $(typeof(x)).")
 ctranspose(x) = conj(transpose(x))
 conj(x) = x
 
diff --git a/base/strings/basic.jl b/base/strings/basic.jl
index 7308123929a073..3beeae923cdc13 100644
--- a/base/strings/basic.jl
+++ b/base/strings/basic.jl
@@ -101,6 +101,8 @@ function length(s::AbstractString)
     end
 end
 
+transpose(s::AbstractString) = s
+
 ## string comparison functions ##
 
 function cmp(a::AbstractString, b::AbstractString)
diff --git a/test/linalg/matmul.jl b/test/linalg/matmul.jl
index 53d1368506e956..769ce7f0cb1c25 100644
--- a/test/linalg/matmul.jl
+++ b/test/linalg/matmul.jl
@@ -320,8 +320,9 @@ end
 immutable RootInt
     i::Int
 end
-import Base: *, promote_op
+import Base: *, transpose, promote_op
 (*)(x::RootInt, y::RootInt) = x.i*y.i
+transpose(x::RootInt) = x
 promote_op(::typeof(*), ::Type{RootInt}, ::Type{RootInt}) = Int
 
 a = [RootInt(3)]