diff --git a/mage/main.go b/mage/main.go
index b51ea95..6925c74 100644
--- a/mage/main.go
+++ b/mage/main.go
@@ -370,6 +370,7 @@ func Invoke(inv Invocation) int {
 	if inv.Dir == "" {
 		inv.Dir = dotDirectory
 	}
+	inv.Dir = filepath.Clean(inv.Dir)
 	if inv.WorkDir == "" {
 		inv.WorkDir = inv.Dir
 	}
diff --git a/mg/runtime.go b/mg/runtime.go
index 678a595..350a55b 100644
--- a/mg/runtime.go
+++ b/mg/runtime.go
@@ -119,7 +119,7 @@ func IgnoreDefault() bool {
 func CacheDir() string {
 	d := os.Getenv(CacheEnv)
 	if d != "" {
-		return d
+		return filepath.Clean(d)
 	}
 	switch runtime.GOOS {
 	case "windows":