diff --git a/Sources/tart/VMStorageHelper.swift b/Sources/tart/VMStorageHelper.swift
index 89a47ad..1e523ae 100644
--- a/Sources/tart/VMStorageHelper.swift
+++ b/Sources/tart/VMStorageHelper.swift
@@ -38,7 +38,8 @@ class VMStorageHelper {
 
 extension NSError {
   func isFileNotFound() -> Bool {
-    return self.code == NSFileNoSuchFileError || self.code == NSFileReadNoSuchFileError
+    return self.domain == NSCocoaErrorDomain &&
+      (self.code == NSFileNoSuchFileError || self.code == NSFileReadNoSuchFileError)
   }
 }
 
diff --git a/Tests/TartTests/CommandBehaviorTests.swift b/Tests/TartTests/CommandBehaviorTests.swift
index c579b0b..b8453c0 100644
--- a/Tests/TartTests/CommandBehaviorTests.swift
+++ b/Tests/TartTests/CommandBehaviorTests.swift
@@ -116,6 +116,12 @@ final class CommandBehaviorTests: XCTestCase {
     }
   }
 
+  func testFileNotFoundRequiresCocoaErrorDomain() {
+    XCTAssertTrue(NSError(domain: NSCocoaErrorDomain, code: NSFileNoSuchFileError).isFileNotFound())
+    XCTAssertTrue(NSError(domain: NSCocoaErrorDomain, code: NSFileReadNoSuchFileError).isFileNotFound())
+    XCTAssertFalse(RuntimeError.VMIsRunning("running").isFileNotFound())
+  }
+
   func testSetDiskRejectsStackedVMBeforeSavingConfig() async throws {
     try await withTemporaryTartHome {
       let vmDir = try VMStorageLocal().create("stacked")