diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 32f5413..c3c5607 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,8 +5,11 @@ on:
 
 jobs:
   build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ macos-latest, windows-latest, ubuntu-latest ]
     name: build and test
-    runs-on: ubuntu-latest
 
     steps:
     - uses: actions/checkout@v2
diff --git a/cleanse.go b/cleanse.go
index 0d828a9..49fed61 100644
--- a/cleanse.go
+++ b/cleanse.go
@@ -1,10 +1,23 @@
 package memoryfs
 
 import (
-	"path/filepath"
 	"strings"
 )
 
 func cleanse(path string) string {
-	return strings.TrimPrefix(strings.TrimPrefix(filepath.Clean(path), "."), separator)
+	path = strings.TrimPrefix(path, separator)
+	var accepted []string
+	for _, part := range strings.Split(path, separator) {
+		switch {
+		case part == "" || part == ".":
+			continue
+		case part == "..":
+			if len(accepted) > 0 {
+				accepted = accepted[:len(accepted)-1]
+			}
+			continue
+		}
+		accepted = append(accepted, part)
+	}
+	return strings.Join(accepted, separator)
 }