diff --git a/src/MethodAnalysis.jl b/src/MethodAnalysis.jl
index d471480..2db9ab2 100644
--- a/src/MethodAnalysis.jl
+++ b/src/MethodAnalysis.jl
@@ -66,17 +66,36 @@ equal(p1::Pair, p2::Pair) = p1.second == p2.second && equal(p1.first, p2.first)
 
 """
     mi = instance(f, types)
+    mi = instance(tt::Type{<:Tuple})
 
-Return the `MethodInstance` `mi` for function `f` and the given `types`.
+Return the `MethodInstance` `mi` for function `f` and the given `types`,
+or for the complete signature `tt`.
 If no version compiled for these types exists, returns `nothing`.
+
+# Examples
+
+```jldoctest; setup=:(using MethodAnalysis)
+julia> f(x, y::String) = 2x; f(x, y::Number) = x + y;
+
+julia> f(1, "hi"); f(1, 1.0);
+
+julia> instance(f, (Int, String))
+MethodInstance for f(::Int64, ::String)
+
+julia> instance(Tuple{typeof(f), Int, String})
+MethodInstance for f(::Int64, ::String)
+```
 """
-function instance(f, types)
-    m = which(f, types)
+function instance(@nospecialize(f), @nospecialize(types))
+    if types isa Tuple
+        m = which(f, types)
+        tt = Tuple{typeof(f), types...}
+        return instance(m, tt)
+    end
     inst = nothing
-    tt = Tuple{typeof(f), types...}
-    visit(m) do mi
+    visit(f) do mi
         if isa(mi, MethodInstance)
-            if mi.specTypes === tt
+            if mi.specTypes === types
                 inst = mi
             end
             return false
@@ -85,6 +104,11 @@ function instance(f, types)
     end
     return inst
 end
+function instance(@nospecialize(types))
+    f, argt = call_type(types)
+    m = which(f, argt)
+    return instance(m, types)
+end
 
 AbstractTrees.children(mi::MethodInstance) = isdefined(mi, :backedges) ? mi.backedges : []
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 8a347f7..db2201e 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -13,6 +13,9 @@ module Outer
     f(x) = 1
     callh(x) = Inner.h(x)
     callcallh(x) = callh(x)
+
+    f2(x, y::String) = 2x
+    f2(x, y::Number) = x + y
 end
 
 
@@ -84,6 +87,11 @@ end
     @test instance(Outer.callcallh, (Int,)) ∈ bes
     @test length(bes) == 5
 
+    Outer.f2(1, "hello")
+    m = which(Outer.f2, (Int, String))
+    tt = Tuple{typeof(Outer.f2),Int,String}
+    @test instance(Outer.f2, (Int, String)) === instance(m, tt) === instance(tt)
+
     hbes = filter(mi->mi.def ∈ methods(Outer.Inner.h), bes)
     @test length(hbes) == 2
     allhbes = with_all_backedges(hbes)