diff --git a/base/file.jl b/base/file.jl
index 094327922dcc5..6d4fca5fda8c5 100644
--- a/base/file.jl
+++ b/base/file.jl
@@ -517,20 +517,27 @@ function mktemp(parent::AbstractString=tempdir(); cleanup::Bool=true)
     return (filename, Base.open(filename, "r+"))
 end
 
+# generate a random string from random bytes
+function _rand_string()
+	nchars = 10
+	A = Vector{UInt8}(undef, nchars)
+	ccall((:SystemFunction036, :Advapi32), stdcall, UInt8, (Ptr{Cvoid}, UInt32), A, sizeof(A))
+
+	slug = Base.StringVector(10)
+	chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	for i = 1:nchars
+	    slug[i] = chars[(A[i] % length(chars)) + 1]
+	end
+	return name = String(slug)
+end
+
 function tempname(parent::AbstractString=tempdir(); cleanup::Bool=true)
     isdir(parent) || throw(ArgumentError("$(repr(parent)) is not a directory"))
-    seed::UInt32 = rand(UInt32)
-    while true
-        if (seed & typemax(UInt16)) == 0
-            seed += 1
-        end
-        filename = _win_tempname(parent, seed)
-        if !ispath(filename)
-            cleanup && temp_cleanup_later(filename)
-            return filename
-        end
-        seed += 1
-    end
+    name = _rand_string()
+    filename = joinpath(parent, temp_prefix * name)
+    @assert !ispath(filename)
+    cleanup && temp_cleanup_later(filename)
+    return filename
 end
 
 else # !windows
diff --git a/test/file.jl b/test/file.jl
index e15807c0adccb..ae3ce717060e0 100644
--- a/test/file.jl
+++ b/test/file.jl
@@ -50,6 +50,18 @@ end
 
 using Random
 
+@testset "that temp names are actually unique" begin
+    temps = [tempname(cleanup=false) for _ = 1:100]
+    @test allunique(temps)
+    temps = map(1:100) do _
+        path, io = mktemp(cleanup=false)
+        close(io)
+        rm(path, force=true)
+        return path
+    end
+    @test allunique(temps)
+end
+
 @testset "tempname with parent" begin
     t = tempname()
     @test dirname(t) == tempdir()