diff --git a/internal/lsp/source/uri.go b/internal/lsp/source/uri.go
index 59429292..4e6d58e6 100644
--- a/internal/lsp/source/uri.go
+++ b/internal/lsp/source/uri.go
@@ -12,8 +12,6 @@ import (
 	"strings"
 )
 
-const fileSchemePrefix = "file://"
-
 // URI represents the full uri for a file.
 type URI string
 
diff --git a/internal/lsp/source/uri_unix.go b/internal/lsp/source/uri_unix.go
new file mode 100644
index 00000000..de7dc3ac
--- /dev/null
+++ b/internal/lsp/source/uri_unix.go
@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !windows
+
+package source
+
+const fileSchemePrefix = "file://"
diff --git a/internal/lsp/source/uri_windows.go b/internal/lsp/source/uri_windows.go
new file mode 100644
index 00000000..00cfce86
--- /dev/null
+++ b/internal/lsp/source/uri_windows.go
@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package source
+
+const fileSchemePrefix = "file:///"
diff --git a/internal/lsp/source/uri_windows_test.go b/internal/lsp/source/uri_windows_test.go
new file mode 100644
index 00000000..aa9025f1
--- /dev/null
+++ b/internal/lsp/source/uri_windows_test.go
@@ -0,0 +1,26 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package source
+
+import (
+	"testing"
+)
+
+func TestURIWindows(t *testing.T) {
+	s := `C:\Windows\System32`
+	uri := ToURI(s)
+	if uri != `file:///C:/Windows/System32` {
+		t.Fatalf("ToURI: got %v want %v", uri, s)
+	}
+	f, err := URI(uri).Filename()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f != s {
+		t.Fatalf("Filename: got %v want %v", f, s)
+	}
+}