diff --git a/Sources/Swiftly/Install.swift b/Sources/Swiftly/Install.swift
index fb43e690..74c0c19b 100644
--- a/Sources/Swiftly/Install.swift
+++ b/Sources/Swiftly/Install.swift
@@ -69,7 +69,7 @@ struct Install: SwiftlyCommand {
             written to this file as commands that can be run after the installation.
             """
         ))
-    var postInstallFile: String?
+    var postInstallFile: FilePath?
 
     @OptionGroup var root: GlobalOptions
 
@@ -156,7 +156,7 @@ struct Install: SwiftlyCommand {
             }
 
             try Data(postInstallScript.utf8).write(
-                to: FilePath(postInstallFile), options: .atomic
+                to: postInstallFile, options: .atomic
             )
         }
     }
diff --git a/Sources/Swiftly/Swiftly.swift b/Sources/Swiftly/Swiftly.swift
index a482fa11..71794236 100644
--- a/Sources/Swiftly/Swiftly.swift
+++ b/Sources/Swiftly/Swiftly.swift
@@ -10,6 +10,16 @@ import SystemPackage
 
 typealias fs = SwiftlyCore.FileSystem
 
+extension FilePath: ExpressibleByArgument {
+    public init?(argument: String) {
+        self.init(argument)
+    }
+
+    public static var defaultCompletionKind: CompletionKind {
+        CompletionKind.file()
+    }
+}
+
 public struct GlobalOptions: ParsableArguments {
     @Flag(name: [.customShort("y"), .long], help: "Disable confirmation prompts by assuming 'yes'")
     var assumeYes: Bool = false
diff --git a/Sources/Swiftly/Update.swift b/Sources/Swiftly/Update.swift
index ff097f74..38cf4c1c 100644
--- a/Sources/Swiftly/Update.swift
+++ b/Sources/Swiftly/Update.swift
@@ -72,7 +72,7 @@ struct Update: SwiftlyCommand {
         written to this file as commands that can be run after the installation.
         """
     ))
-    var postInstallFile: String?
+    var postInstallFile: FilePath?
 
     private enum CodingKeys: String, CodingKey {
         case toolchain, root, verify, postInstallFile
@@ -138,7 +138,7 @@ struct Update: SwiftlyCommand {
                 """)
             }
 
-            try Data(postInstallScript.utf8).write(to: FilePath(postInstallFile), options: .atomic)
+            try Data(postInstallScript.utf8).write(to: postInstallFile, options: .atomic)
         }
 
         if pathChanged {