diff --git a/system/syscall_unix.go b/system/syscall_unix.go
index 5005476..f1497c5 100644
--- a/system/syscall_unix.go
+++ b/system/syscall_unix.go
@@ -6,6 +6,6 @@ import "syscall"
 
 // Unmount is a platform-specific helper function to call
 // the unmount syscall.
-func Unmount(dest string) {
-	syscall.Unmount(dest, 0)
+func Unmount(dest string) error {
+	return syscall.Unmount(dest, 0)
 }
diff --git a/system/syscall_windows.go b/system/syscall_windows.go
index 3a3a55b..b3b94cb 100644
--- a/system/syscall_windows.go
+++ b/system/syscall_windows.go
@@ -2,5 +2,6 @@ package system
 
 // Unmount is a platform-specific helper function to call
 // the unmount syscall. Not supported on Windows
-func Unmount(dest string) {
+func Unmount(dest string) error {
+	return nil
 }