diff --git a/src/TypeCheck.jl b/src/TypeCheck.jl
index 238076b..7b74e74 100644
--- a/src/TypeCheck.jl
+++ b/src/TypeCheck.jl
@@ -225,7 +225,7 @@ type MethodSignature
   returntype::Union(Type,TypeVar) # v0.2 has TypeVars as returntypes; v0.3 does not
 end
 MethodSignature(e::Expr) = MethodSignature(argumenttypes(e),returntype(e))
-function Base.writemime(io, ::MIME"text/plain", x::MethodSignature)
+function Base.writemime(io::IO, ::MIME"text/plain", x::MethodSignature)
   println(io,"(",join([string(t) for t in x.typs],","),")::",x.returntype)
 end
 
@@ -234,7 +234,7 @@ type FunctionSignature
   name::Symbol
 end
 
-function Base.writemime(io, ::MIME"text/plain", x::FunctionSignature)
+function Base.writemime(io::IO, ::MIME"text/plain", x::FunctionSignature)
   for m in x.methods
     print(io,string(x.name))
     display(m)
@@ -291,7 +291,7 @@ type LoopResult
   LoopResult(ms::MethodSignature,ls::Vector{(Symbol,Type)}) = new(ms,unique(ls))
 end
 
-function Base.writemime(io, ::MIME"text/plain", x::LoopResult)
+function Base.writemime(io::IO, ::MIME"text/plain", x::LoopResult)
   display(x.msig)
   for (s,t) in x.lines
     println(io,"\t",string(s),"::",string(t))
@@ -303,7 +303,7 @@ type LoopResults
   methods::Vector{LoopResult}
 end
 
-function Base.writemime(io, ::MIME"text/plain", x::LoopResults)
+function Base.writemime(io::IO, ::MIME"text/plain", x::LoopResults)
   for lr in x.methods
     print(io,string(x.name))
     display(lr)
@@ -383,7 +383,7 @@ type CallSignature
   name::Symbol
   argumenttypes::Vector{AType}
 end
-function Base.writemime(io, ::MIME"text/plain", x::CallSignature)
+function Base.writemime(io::IO, ::MIME"text/plain", x::CallSignature)
   println(io,string(x.name),"(",join([string(t) for t in x.argumenttypes],","),")")
 end
 
@@ -392,7 +392,7 @@ type MethodCalls
   calls::Vector{CallSignature}
 end
 
-function Base.writemime(io, ::MIME"text/plain", x::MethodCalls)
+function Base.writemime(io::IO, ::MIME"text/plain", x::MethodCalls)
   display(x.m)
   for c in x.calls
     print(io,"\t")
@@ -405,7 +405,7 @@ type FunctionCalls
   methods::Vector{MethodCalls}
 end
 
-function Base.writemime(io, ::MIME"text/plain", x::FunctionCalls)
+function Base.writemime(io::IO, ::MIME"text/plain", x::FunctionCalls)
   for mc in x.methods
     print(io,string(x.name))
     display(mc)